A spinoff of my viral s'mores cookie bar that I've been making for years...but STUFFED. A hidden layer of graham crackers and a full jar of marshmallow fluff get tucked inside two layers of cookie dough, so every single square has that campfire pull when you bite in.
tester review ★★★★★
"OMG these are one of the best things I've ever had. I LOVE s'mores but these take them to a whole new level. I'm already sad about them being gone and they aren't even gone yet! 10/10".
- Anonymous family member
Holy cow, these are GOOD.
I made these a few weeks ago when I was back in Iowa and ended up making two pans over the course of the week.
I had been dreaming of making a layered version of my popular s'more cookie bar recipe for a while, and after a few tests, perfection was achieved.
Here's why I love these:
- One 9×13 pan, 24 bars: Enough for a cookout, bake sale, or pool party with leftovers for the lunchbox.
- No campfire, no mess. All of the s'mores nostalgia with none of the sticky marshmallow-on-a-stick chaos.
- Pantry-friendly. Almost entirely staples plus one jar of fluff and a Hershey's bar.
After 15 years of recipe-developing and a full cookbook of 9x13" pan baking (One Crafty Pan), I have learned one thing about s'mores desserts: the gooier, the better.
Video
Watch me make this on Instagram!
Watch me make this on Instagram! You'll see how easy it is to make these stuffed s'more bars!
what you need
Ingredient Notes & Substitutions
- Marshmallow fluff : Use one 13 oz jar (the bigger jar). The first time I made these, I used the 7 oz jar and then my sister made me add more. And it was a good move. If you want to use mini marshmallows, make my other s'more cookie bars instead.
- Graham crackers: 16 squares get crushed into the cookie dough for flavor (~1 cup of crumbs), and the remaining 20ish squares form the hidden interior layer.
- Chocolate Chips: I prefer semi-sweet chocolate chips for these so that they're not overly sweet, but you can use a mix of your favorite kinds.
- Hershey's bar (for finishing): I like to press one bar in the hot bars so that chocolate softens but doesn't melt entirely.
How to Make Stuffed S'mores Bars
These come together in three layers: a bottom cookie dough base, a graham-cracker-and-marshmallow-fluff middle, and a cookie dough top.
Prep the pan and crush the grahams
Preheat oven to 350°F. Spray a 9×13 pan with nonstick spray and line with parchment, leaving overhang on two sides for lifting later.
Put 8 graham cracker rectangles into a zip-top bag and crush with a rolling pin into fine crumbs (about 1 cup). Set crumbs aside.
Mix the cookie dough
Melt butter in a microwave-safe bowl until just melted. Transfer to a large bowl and whisk with the brown sugar and granulated sugar until combined.
Mix in the eggs and vanilla extract. Add the baking soda, baking powder, and salt and mix again. Stir in the all-purpose flour and graham cracker crumbs until no flour remains. Fold in the semi-sweet chocolate chips.
Layer all the delicious goodness.
- Scoop half of the dough into the prepared pan in small chunks. Press and smooth into one even layer, reaching all four corners.
- Lay 8-9 whole graham cracker rectangles over the dough in a single layer, breaking pieces to fill any gaps.
- Spoon the entire 13 oz jar of marshmallow fluff over the grahams and spread gently. It's OK if some graham crackers break.
- Flatten small portions of the remaining dough between your fingers into thin discs (about palm-sized). Drop them onto the fluff layer, covering as much surface as you can while leaving a few small windows of fluff peeking through.
Tip: lightly spray your fingertips with cooking spray so the dough doesn't stick to your hands.
Step 6 · Bake, finish, and cool
Bake at 350°F for 18-20 minutes, just until the marshmallow windows turn a light golden brown. Do not overbake; the center should still look slightly soft. The second the pan comes out, press pieces of a Hershey's bar over the top so they soften into the warm cookie. Cool completely in the pan (about 2 hours, or 1 hour at room temperature plus 30 minutes in the fridge) before slicing into 24 bars.
Storage & Freezing
- Room temperature: Stuffed S'mores Bars stay soft and gooey in an airtight container at room temperature for up to 4 days. After that they start to dry out.
- Freezer: Wrap individual bars in plastic wrap and store in a freezer bag for up to 2 months. Thaw at room temperature. The marshmallow fluff does get stickier, so it's not the best if you're tryign to impress with aesthetics.
gift it!
How to package these as a gift!
Cut the bars into clean squares with a hot knife (run it under hot water, wipe dry between cuts), then stack them in a plastic treat bag. If stacking, layer a small square of parchment between each one to prevent sticking.
As a graphic designer and baker, I design printable gift tags (like the one below! and labels that live inside my Crafty Baker's Club membership...print, trim, tie on with bakers' twine, done.
melissa's tips
Tips & Variations
- Want even more chocolate? Press extra chocolate chunks into the top layer of dough before baking, in addition to the Hershey's finish. Note! Don't put the hershey bar pieces on before baking; they will shrivel up and look terrible.
- Make it a flavor remix: swap honey grahams for chocolate grahams for double-chocolate s'mores bars.
- Thicker bars? Use a 9×9 pan and add 5-8 minutes to the bake time. If doing this, use 7-ounces of fluff instead of 13-ounces.
- Don't skip the cool: The single biggest mistake people make with cookie bars is cutting them while warm. The marshmallow layer needs time to set in order to get clean cuts. That said, these are great straight from the oven so dig in with a spoon ;)
Frequently Asked Questions
You can! If you want to do that, I recommend following the instructions in my s'more cookie bars recipe instead.
The marshmallow layer needs to fully cool and set, which takes about 2 hours at room temperature (or 1 hour plus 30 minutes in the fridge). For bakery-clean squares, use a hot, dry knife and wipe the blade between cuts.
Yes! Swap a 1:1 gluten-free all-purpose flour blend and use gluten-free graham crackers for both the crushed and whole layers. The texture stays very close to the original. For an even better texture, use half 1:1 gluten-free flour and half almond flour.
Bake them up to 2 days ahead. Cool completely, cut into bars, and store in an airtight container at room temperature. They are arguably better on day two once the marshmallow layer fully sets into the cookie.
The marshmallow fluff peeking through the top dough windows should turn light golden brown, and the edges of the bars should look set. The center will still look slightly soft, as they will firm up as they cool.
Looking for more easy summer desserts?
Stuffed S'more Cookie Bars
Ingredients
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Instructions
- Preheat oven to 350°F. Spray a 9×13 pan with nonstick cooking spray and line with parchment.
- Add 16 graham cracker squares to a large zip-top bag and crush with a rolling pin until you have fine crumbs (about 1 cup). Set aside.
- Melt 1 cup unsalted butter in a microwave-safe bowl for 30-60 seconds until just melted. Transfer to a large bowl and whisk in 1 cup light brown sugar and ½ cup granulated sugar for 1 minute until combined.
- Mix in 2 large eggs and 2 teaspoons vanilla extract. Add the 1 teaspoon baking soda, ½ teaspoon baking powder, and ½ teaspoon salt and mix again. Stir in 2 ½ cups all-purpose flour and graham cracker crumbs until no flour remains. Fold in all the 1 cup semi-sweet chocolate chips.
- Drop half of the cookie dough in small chunks across the prepared pan. Press and smooth into an even layer, making sure to reach all the corners.
- Lay the remaining 20 graham cracker squares in a single layer over the dough, arranging them to cover as much surface as possible.
- Dollop 13 ounces marshmallow fluff over the graham cracker layer, then spread it gently into an even layer. Tip: lightly spray your spatula with cooking spray to prevent sticking.
- Take the remaining cookie dough and flatten small portions between your fingers into thin discs. Drop and place them over the marshmallow fluff layer, covering as much of the surface as possible while still leaving some "holes" of marshmallow fluff. Pinch and press edges together where you can.
- Bake at 350°F for 18-20 minutes or until the marshmallow fluff just starts to turn a light golden brown. Do not overbake. After removing from the oven, press on pieces of 1 Hershey bar.
- Allow to cool completely in the pan before cutting into 24 bars. The marshmallow layer sets as it cools and makes cutting much cleaner.
Did you make this?
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Delicious! And makes it very easy to serve/share as a summer/potluck dessert. However, my husband and I just ate these straight out of the pan because it was so good and way less messy than making full s’mores pieces 😂 1000% would make again!
I made these bars to bring to a lunch date. Everybody loved them and wanted the recipe. I had to give some to my neighbors and freeze the rest before I ate the rest of the pan. 10/10.
These were a hit!
These are DANGEROUSLY good. I could easily eat multiple in one sitting but trying not to! I was already a big fan of the original s’mores bars (my first recipe to ever try of Melissa’s!) but she knocked it out of the park with this version!! My marshmallow didn’t fully set (we only had marshmallow crème and not fluff at our grocery store) so I sprayed a plastic food scraper with Pam for cutting and that helped a ton. Will definitely be making these over and over again.