Homemade Cosmic Brownies (Tiktok Viral)

These thick, fudgy homemade cosmic brownies are 10x better than storebought and went TikTok viral with over 13 million views! Topped with a creamy homemade chocolate ganache (made without heavy cream!) and rainbow chip sprinkles, these brownies are truly out-of-this-world delicious.

Be sure to read the post for important tips, step-by-step photos, a discount code for the rainbow sprinkles, and general FAQ's!

Why These Homemade Cosmic Brownies are 10x Better Than Storebought

1. Super Thick: Instead of the thin, store-bought Little Debbie brownies, I developed this recipe to be THICK when made in a 9x13 pan! No paper thin brownies here.
2. Ultra Fudgy: The combination of melted butter, oil, cornstarch, an extra egg yolk, and Hershey's cocoa gives it that iconic fudgy Cosmic Brownie texture.
3. Simple ganache without heavy cream: While most cosmic brownie recipes require you to use heavy cream for the frosting, I very rarely have it stocked in my fridge. So I really wanted to develop this recipe using a milk & butter ganache so that you can skip that extra step to the store (it's a bit softer in texture than ganache using cream) but tastes just as good...if not better! I also have a rich brownie frosting, if you're wanting to avoid the ganache all together!
4. Tastes WAY Better: I hate to say it but the cosmic brownies I loved as a kid just don't taste the same anymore (they taste like plastic and not like chocolate!). This homemade version has a rich, fudgy chocolate flavor that you'll love.

Watch my viral Tiktok video below!

Homemade Cosmic Brownie Ingredient Overview:

This is just an overview, click here to jump down to full recipe card for the recipe amounts and condensed recipe instructions.

• Unsalted Butter (you will be melting this so no need for it to be softened to room temperature!)
• Granulated Sugar & Brown Sugar
• Eggs: You'll need 3 eggs + 1 extra yolk (to make the brownies nice & chewy!)
• Vanilla Extract
• Vegetable Oil: The oil also keeps the brownies moist & fudgy (if you leave it out, your brownies will be more cake-like and dry).
• Cornstarch: This is the other secret ingredient to moist & fudgy brownies! If you have a corn allergy, you can leave it out.
• Salt
• Baking Soda
• Hershey's Cocoa Powder: I tested this recipe using Hershey's 100% Cacao Natural Unsweetened. I highly recommend using this exact brand or a high quality cocoa, as "off brands" or cheaper cocoa does not often taste good (you've been warned!).
• All-Purpose Flour
• Rainbow Chip Sprinkles: you can get these on Amazon (some craft stores & grocery stores also carry them!).
• For Chocolate Ganache: Semi-sweet chocolate chips (see next section for notes on brands!), butter, milk (ideally whole milk or 2% but more notes on milk in the recipe card "notes" section below).

Love this copycat recipe for Cosmic Brownies & craving more? I'm working on a new series of Little Debbie recipes, but in the meantime check out my Homemade Oatmeal Creme Pies and quick Homemade Star Crunch recipe that you can make in the microwave!

Where to buy the sprinkles?

I get my rainbow chip sprinkles on Amazon! It's a big, bulk-sized bag that will last you for a while! It also comes with a resealable bag for easy storing.

And! You can use them on my other cosmic recipes: Fudgy Cosmic Brownie Cookies, Christmas Tree Brownies, or even just use as an ice cream topping on my No Churn Chocolate Ice Cream!

Buy On Amazon

Easy Chocolate Ganache Using Milk (i.e. without heavy cream!)

Read this important section for lots of notes & tricks!

Heavy Cream vs. Milk: I debated between using heavy cream or milk for this ganache but since I rarely have heavy cream in my fridge...I figured most of you don't either! So I opted for ease & simplicity and developed this recipe using milk and butter instead (the butter replaces the fat from the heavy cream!). The result is a smooth, creamy frosting that is so delicious and soft.

Chill To Firm Ganache: Because we're not making a traditional ganache with heavy cream, the frosting won't totally harden at room temperature so it's important to chill the finished brownies. After spreading the frosting on the brownies, refrigerate for 1-2 hours for the frosting to set (do this before cutting, if you're trying to get clean edges!). The ganache will start to soften at room temperature, so I recommend storing them in the refrigerator to keep it firm.

Differences In Chocolate Chip Brands: We also found that the brand of semi-sweet chocolate chip you use will impact how firm the ganache sets up in the fridge. We tested this ganache using 4 different common semi-sweet chocolate chip brands. Nestle Toll House was #1 in producing the firmest ganache, Ghiradelli #2, Hershey's #3, Costco brand #4. All are comparable taste-wise (I like the flavor of Ghiradelli the best!) but they all do firm up a bit differently. 

Want a more firm ganache that hardens? If you want the frosting to stay "hard" at room temperature, you will need to use heavy cream. To make a firm ganache, follow the instructions in the recipe card below but use ½ cup heavy cream and 1.5 cups chocolate chips (no butter).

How To Make Cosmic Brownies (step by step photos!)

This is just an overview showing step-by-step photos, click here to jump down to full recipe card with exact instructions.

Step 1: Melt Butter & Sugars, then Mix Brownie Batter

Preheat the oven to 350° degrees. Follow the instructions in the recipe card below to make the brownie batter, carefully reading each step (take note that you will be melting the butter and sugars together at first!).

Step 2: Spread Into Pan

Spray a light-colored metal 9x13 pan with nonstick cooking spray, then press on a piece of parchment paper to cover the bottom and long sides to create a "parchment sling". This will help you lift the brownies out of the pan so that you can cut them nicely. Spread brownie batter into the prepared pan until smooth.

Note: baking these in glass or dark metal pans may cause them to overbake and become bitter. If that's the only pan you have, lining with parchment on all sides becomes more crucial. You will also likely need to bake them for less time to prevent overbaking.

Step 3: Bake

Bake for 24-26 minutes and let them cool completely before adding any glaze or frosting. After the pan is no longer hot to the touch, you can also speed up the cooling process by placing the pan in the fridge. In the meantime, move to step 4 to make the chocolate ganache!

Tip: Be careful not to overbake the chocolate brownies! Check to make sure they are done by inserting a toothpick into the middle or gently shaking the pan to ensure the center is not jiggly. If the toothpick comes out clean, then they are finished baking. If you bake them too long, they won't have the irresistible fudgy texture you want.

Step 4: Make Easy Ganache

While the brownies are cooling, prepare the easy chocolate ganache! In a medium-sized bowl, place chocolate chips and chopped butter. In a separate medium-sized bowl or large liquid measuring cup, heat milk in the microwave for 2 minutes (it's important that your measuring cup or bowl is at least 3x taller than the milk line, as it will expand when it's heating and can easily overflow). You can also heat this on the stove; remove once it begins to steam.

Use a hot pad to carefully remove milk from the microwave and pour over the chocolate chips and butter (do not stir yet!). Allow to sit on the counter for about 3 minutes, then stir until smooth and creamy. It may take a few minutes for it to come together; it often looks separated at first. Allow to cool for about 30 minutes before pouring over cooled brownies.

Step 5: Decorate Brownies

Once brownies are cooled, give the ganache a quick stir then spread over the brownies. Immediately top with rainbow chip sprinkles (or any other sprinkles you have!). Place in refrigerator for 1-2 hours to help the frosting harden (you can speed this up by putting in the freezer!).

Tip: As I said earlier in this post, this frosting is made without heavy cream so it's not going to totally harden at room temperature. This is why I recommend storing the brownies in the fridge after frosting.

Step 6: Cut & Enjoy!

If you want really clean edges & slices, you will need to refrigerate the frosted brownies for at least 2 hours for the frosting to set. Or freeze for an hour. It's best to cut these straight from the fridge or freezer, as that is when you'll get the cleanest slice.

After they sit out at room temperature, the frosting will start to get softer so I recommend storing in the fridge if you want them to stay looking fresh & fine ;)

Tip: To get a clean edge, use a large chef's knife, cut straight down, then wipe off in between each cut (do not "saw" through the brownies back in forth). This will help you get that crisp cut like the real Little Debbie cosmic brownies!

Storage & Freezing

How long do these fudgy brownies last?

In order for the brownies to last the longest (and keep their amazing taste & texture), I suggest you store them in an airtight container for 3-4 days. If you want the frosting to stay hardened, store them in the refrigerator. If stored properly, they'll stay good for 4-5 days.

Can cosmic brownies be frozen?

They sure can! The fudgy texture & soft frosting actually makes these so good out of the freezer (they're not rock hard!). If you want to keep the frosting looking nice, freeze the brownies (unwrapped and uncovered) for 1-2 hours then transfer them to an airtight container. This will allow the frosting to freeze so that it doesn't smudge when you store them.

These fudgy brownies will keep in the freezer for 1-2 months (any longer, and they tend to dry out).

Frequently Asked Questions:

New! Cosmic Christmas Tree Brownies

Turn these cosmic brownies into adorable cosmic brownie trees for the holidays!

4.88 from 607 votes

Homemade Cosmic Brownies (TikTok Viral)

Makes: 24

Print Pin Ad-Free Club

Prep Time: 15 minutes mins

Total Time: 1 hour hr

These thick, fudgy homemade cosmic brownies are 10x better than storebought! Topped with a creamy homemade chocolate ganache (made without heavy cream!) and rainbow chip sprinkles, these brownies are truly out-of-this-world delicious.

Recipe by Melissa Rose

Ingredients

 

1x2x3xAdd your own

• ¾ cup unsalted butter, (i.e 1.5 sticks; you will be melting this)
• 1 ½ cups granulated sugar
• ½ cup light brown sugar
• 3 large eggs + 1 egg yolk
• 1 tablespoon vanilla extract
• 1 teaspoon salt
• ¼ teaspoon baking soda
• 2 tablespoons cornstarch
• 1 ½ cups Hershey's cocoa powder (100% cacao natural unsweetened), I highly recommend using this specific cocoa or another quality cocoa. Off-brand cocoa often tastes bad so use at your own risk...you've been warned!
• 1 cup all-purpose flour
• ¼ cup vegetable oil

Easy Chocolate Ganache (see notes section below for a firmer, traditional ganache using heavy cream)

• 1 ½ cups semi-sweet chocolate chips, (i.e. 12 ounce bag) *see notes section below for notes on certain brands; we found Nestle Toll House or Ghiradelli brands firm up the best
• 6 tablespoons unsalted butter, chopped into small cubes
• ½ cup whole milk, (you can also use 2% or 1% but the ganache will be less firm so you will need to refrigerate and/or freeze brownies so frosting sets; see notes below)

Topping

• Rainbow chip sprinkles, you can get the Wilton brand at most craft stores or on Sweetapolita (use code DESIGNEATSPRINKS15" for 15% site-wide!)

⭐️ Before you begin! If you make this, will you do me a huge favor afterwards and leave a review and rating letting me know how you liked this recipe? This helps my small business thrive so I can continue providing free recipes and high-quality content for you.

Instructions

 

To Make Brownies:

1. Before you start, be sure to read through the tips & tricks in the post above for ingredient notes, step-by-step photos, and FAQ's!
2. Preheat oven to 350° F.
3. In a large microwave-safe bowl, add ¾ cup unsalted butter, 1 ½ cups granulated sugar, and ½ cup light brown sugar. Microwave for 2 minutes, stir, then microwave for 30 more seconds. Carefully remove bowl from microwave and stir until smooth. Let cool for 2-3 minutes.
4. To the butter and sugar mixture, stir in the 3 large eggs + 1 egg yolk, 1 tablespoon vanilla extract, 1 teaspoon salt, ¼ teaspoon baking soda, and 2 tablespoons cornstarch. Once combined, mix in 1 ½ cups Hershey's cocoa powder (100% cacao natural unsweetened) and 1 cup all-purpose flour until just combined (I recommend mixing by hand to prevent from overmixing). Stir in ¼ cup vegetable oil.
5. Spray a light metal 9x13 pan with nonstick cooking spray, then press on a piece of parchment paper to cover the bottom and long sides to create a parchment sling (photo in post above!). This will help you lift the brownies out of the pan so that you can cut them nicely. Spread brownie batter into the prepared pan until smooth.

   Note: baking these in glass or dark metal pans may cause them to overbake and become bitter. If that's the only pan you have, lining with parchment on all sides becomes more crucial. You will also likely need to bake them for less time to prevent overbaking.
6. Bake at 350° F for 24-26 minutes or until center looks set and no longer jiggles when you gently shake the pan (do not overbake). Let cool completely in pan (once the pan is no longer hot to the touch, you can speed up cooling by placing pan in refrigerator.

To Make Easy Chocolate Ganache

1. Before you begin: Note that the ganache will not completley "harden" as a traditional ganache with heavy cream would. See notes section below for tips & tricks, as well as an alternate recipe using heavy cream.
2. In a medium-sized bowl, place 1 ½ cups semi-sweet chocolate chips and chopped 6 tablespoons unsalted butter.
3. In a separate medium-sized bowl or large liquid measuring cup, heat ½ cup whole milk in the microwave for 1 ½ - 2 minutes, or until it begins to bubble (it's important that your measuring cup or bowl is at least 3x taller than the milk line, as it will expand when it's heating and can easily overflow). You can also heat this on the stove; remove it once it begins to steam.
4. Use a hot pad to carefully remove milk from the microwave and pour over the chocolate chips and butter (do not stir yet!). Allow to sit for about 3 minutes, then use a whisk to stir until smooth and creamy. It may take a minute or two for it to come together; it often looks separated at first. Allow to cool for about 30 minutes before pouring over cooled brownies.

To Decorate:

1. Once brownies are cooled, re-stir the ganache and spread over brownies. Immediately top with rainbow chip sprinkles (or any other sprinkles you have!). Place in refrigerator for 1-2 hours to help the frosting harden (you can speed this up by putting in the freezer!).

   Use a large knife to slice bars ( I highly recommend that your bars are chilled or frozen before slicing to ensure a clean cut).
2. Storage: Refrigerate the frosted bars. You can also keep at room temperature for up to 1 day (just note the frosting will soften). They get even better & fudgier on Day 2!

Notes from Melissa

Wil the ganache harden?: Since we're doing a simple ganache using butter & milk, the ganache won't be as "hard' at room temperature as a traditional ganache would be (see next note for an alternate recipe!). Because of this, I recommend storing the frosted brownies in the fridge if you don't want the frosting to soften. After spreading on the ganache and adding the sprinkles, refrigerate for 1-2 hours for the frosting to set (before cutting, if you're trying to get clean edges!). The ganache will start to soften at room temperature, so I recommend storing them in the refrigerator or freezer to keep it firm.

Want a more firm ganache that hardens? If you want the frosting to stay “hard” at room temperature, you will need to use heavy cream. To make a firm ganache, follow the instructions below but use ½ cup heavy cream and 1.5 cups chocolate chips (no butter).

Can I use 2% or 1% milk instead of whole milk? We knew you'd ask, so we tested the ganache with both! Both actually work just fine but refrigerating or freezing the frosted bars becomes more crucial, as the ganache doesn't firm up as well.

A note on chocolate chip brands: The brand you use in the ganache will impact how firm it will set in the fridge. We tested this ganache using 4 different common semi-sweet chocolate chip brands. Nestle Toll House was #1 in producing the firmest ganache, Ghiradelli #2, Hershey's #3, Costco brand #4. All are comparable taste-wise but do firm up a bit differently. You can see my full comparison here!

Cocoa Powder:  I tested this recipe using Hershey’s Unsweetened Cocoa powder, as it’s my favorite cocoa for brownies. Take note that different brands may cause the brownie taste and texture to be a bit different.

Nutrition is just an estimate and calculated with an automated system.

Nutrition

Calories: 253kcal, Carbohydrates: 31g, Protein: 3g, Fat: 14g, Saturated Fat: 9g, Polyunsaturated Fat: 1g, Monounsaturated Fat: 4g, Trans Fat: 1g, Cholesterol: 44mg, Sodium: 123mg, Potassium: 175mg, Fiber: 3g, Sugar: 22g, Vitamin A: 308IU, Calcium: 30mg, Iron: 2mg

Did you make this?

I'd LOVE to hear your thoughts! Leave a review & photo of your creation and be sure to mention @DesignEatRepeat or tag #DesignEatRepeat on Instagram!

Rate this Recipe Follow @DesignEatRepeat