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

• Super Thick: Instead of the thin, store-bought Little Debbie brownies, I developed this recipe to be THICK when made in a 9×13 pan! No paper thin brownies here.
• 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.
• 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!
• 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!

@designeatrepeat

Cosmic brownies…but 10x better 🌈💪 Tap green button on video for recipe! recipes baking littledebbie treatyourself cosmicbrownie

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Copycat Cosmic Brownie: Tips for Success

• Mix by hand: The secret to fudgy brownies is to mix the brownies by hand so that you don’t whip too much air into the batter. If you do use an electric mixer, beat it on a very slow speed and only mix until just combined.
• Use a light-colored metal pan, lined with parchment: Glass pans bake too slow and can cause the edges to overbake and get hard before the center fully bakes. While dark-colored pans will bake brownies too fast, causing dry and overbaked brownies (that can taste bitter). A light-metal 9×13 pan is what I recommend for this recipe.
• Refrigerate the bars after frosting: Since we’re doing a simple ganache using butter & milk, the ganache won’t be as “hard’ at room temperature than a traditional ganache would be (scroll for more notes on the ganache!). So I recommend storing the frosted brownies in the fridge if you don’t want the frosting to soften.
• Use a high quality cocoa powder: I tested this recipe using Hershey’s 100% Cacao Natural Unsweetened Cocoa powder, as it’s my favorite cocoa for brownies. I highly recommend using this exact brand or another high-quality cocoa, as “off brands” or cheaper cocoa often tastes like “fake chocolate” and will not taste good (you’ve been warned!). If you use a different brand or type of cocoa, just take note that the taste, texture, and appearance may significantly change.

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 Sweetapolita (use promo code “DESIGNEATSPRINKS15“ for 15% site-wide) or Amazon (although they don’t keep the smaller bottoles stocked well).
• For Chocolate Gananche: 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!

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 1/2 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!).

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Step 2: Spread Into Pan

Spray a light-colored metal 9×13 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.

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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: 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:

What type of cocoa can I use?

I tested this recipe using Hershey’s 100% Cacao Natural Unsweetened. I highly recommend using this exact brand or another high-quality cocoa, as “off brands” or cheaper cocoa often tastes like “fake chocolate” and will not taste good (you’ve been warned!). If you use a different brand or type of cocoa, just take note that the taste, texture, and appearance may change.

What candies are on Cosmic Brownies?

The real Little Debbie cosmic brownie sprinkles are called “rainbow chip sprinkles” but you can also just use mini M&M’s! I’ve included a few places below where you can find rainbow sprinkle sprinkles.

• Amazon: You can get Wilton rainbow chip sprinkles on Amazon
• Sweetapolita: use promo code “DESIGNEATSPRINKS15“ for 15% site-wide! Search “bit chips” on her site for the cute options…she even has pastel ones!
• Craft stores like Michaels or Joanns also often have them! A reader also mentioned they’ve seen them at Walmart!

Do you need an electric mixer?

To ensure your brownies are dense & chewy, I recommend mixing this by hand! Using an electric or stand mixer will make it quicker, but be sure not to beat the batter very much!

Will this frosting harden?

Be sure to read the post above for more specifics about this easy ganache or see my chocolate chip comparison post! The short answer is no, because we’re using milk & butter instead of heavy cream, these will not completely harden at room temperature so you’ll want to store them in the fridge if you want the frosting to stay looking nice.

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 1/2 cup heavy cream and 1.5 cups chocolate chips (no butter).

I personally like the taste of the milk & butter ganache (it’s creamier & tastier) but if you need to transport these or stack (between parchment paper), it’s best to use a traditional chocolate ganache that uses heavy cream.

What are cosmic brownies?

Cosmic brownies are a popular packaged treat in the United States consisting of a thin, fudgy brownie with a chocolate coating and rainbow sprinkles. Made by the company “Little Debbie”, cosmic brownies & their whole array of snack treats are nostalgic childhood lunchbox treats that can be found at most grocery stores or gas stations in the US. I’ve gotten this question from people outside of the US so I figured I’d throw in a little info for my overseas friends!