Thick, chewy and extra gooey—these s’mores cookie bars capture everything you love about the classic campfire treat. The cookie dough is partially made with crushed graham crackers for authentic s’mores flavor, and the dough is filled with a thick layer of milk chocolate and marshmallow fluff.
These s’mores cookie bars are a summer favorite—and honestly worth making any time of year. The base is a simple cookie dough, similar to blondie or classic chocolate chip cookie dough, with some of the flour replaced by crushed graham crackers for that unmistakable s’mores note. A layer of milk chocolate sits on the bottom dough, topped with a generous spread of marshmallow fluff, then more cookie dough is added on top.
The result is a very thick bar with a generous chocolate core and pockets of gooey marshmallow throughout.
Tip: Slice the bars while warm for an ooey-gooey, spoon-worthy treat. If you prefer cleaner slices like in the photos, let the bars cool completely before cutting.
Making S’mores Cookie Bars
Begin by preparing the graham cookie dough.
- Whisk together melted butter, brown sugar and granulated sugar until the butter is fully incorporated and no longer sits on top of the sugars.
- Whisk in the egg, the extra egg yolk and vanilla extract. The additional yolk keeps the bars chewy.
- Stir in the flour and salt until combined; salt balances the sweetness.
- Fold in the crushed graham crumbs until evenly distributed.
Next, assemble the bars.
- Reserve about 1 cup of the cookie dough for the top layer.
- Press the remaining dough evenly into the bottom of a lined 8×8-inch pan.
- Place an even layer of milk chocolate over the bottom cookie layer.
- The author used Hershey’s milk chocolate bars: three full bars plus pieces of a fourth to cover the layer evenly.
- Spread about 1½ cups of marshmallow fluff over the chocolate.
- Make sure the chocolate is beneath the fluff; this helps with slicing after baking.
- Scoop the reserved dough into small balls, flatten them, and place them over the marshmallow layer to cover as much as possible.
- It’s okay if some marshmallow shows through.
Bake the bars for about 30–35 minutes at 350°F (180°C). The top should turn golden brown. If any marshmallow is exposed, it will puff slightly and create pockets of gooey marshmallow; if fully covered by dough, the marshmallow layer remains more even.
Ingredient Substitutions
Graham crumbs: If you can’t find graham crackers (for example in the UK or Australia), crushed digestive biscuits are a good substitute.
Chocolate: Use your preferred chocolate—milk, dark or semi-sweet bars all work. Chocolate chips are an option, but whole chocolate bars melt into a more s’mores-like layer.
Marshmallow fluff: Do not substitute with marshmallows. Marshmallows will melt into the dough and won’t create the same gooey center as marshmallow fluff.
More s’mores treats to enjoy:
- Easy S’mores Bars — bars with a graham cracker crust
- Golden Graham S’mores Bars — a crunchy, nostalgic variation
S’mores Cookie Bars
Equipment
- 8×8 inch (20×20 cm) pan
Ingredients
- ¾ cup unsalted butter, melted and cooled slightly
- ½ cup brown sugar (light or dark)
- ¼ cup granulated sugar
- 1 large egg
- 1 large egg yolk (in addition to the whole egg)
- 2 teaspoons vanilla extract
- 1½ cups all-purpose flour
- ¼ teaspoon salt
- ½ cup graham crumbs (about 5 sheets of graham crackers)
- 2 XL Hershey’s milk chocolate bars (or four 100 g bars, or about 1½ cups chocolate chips)
- 1½ cups marshmallow fluff (about half of a 16 oz container)
Instructions
- Preheat the oven to 350°F (180°C). Line an 8×8 inch pan with parchment paper, leaving an overhang for easy removal.
Make the Cookie Dough
- In a large bowl, whisk together the melted butter, brown sugar and granulated sugar until the butter is absorbed.
- Whisk in the egg, additional egg yolk and vanilla until combined.
- Stir in the flour and salt until no lumps remain.
- Fold in the graham crumbs until evenly mixed into the dough.
Assemble the Bars
- Scoop out 1 cup of dough and set aside for the top layer.
- Press the remaining dough into the bottom of the prepared pan.
- Place a layer of chocolate over the dough. Break bars as needed to create an even layer or sprinkle with chocolate chips.
- Spoon the marshmallow fluff over the chocolate and spread into an even layer.
- Form the reserved dough into small dollops (1–2 tablespoons each), flatten them slightly, and place them atop the marshmallow layer, covering as much as possible.
Bake & Slice
- Bake in the center of the preheated oven for 30–35 minutes, until the top is golden and exposed marshmallow begins to puff.
- Cool the bars in the pan. Four hours will keep them gooey; for the cleanest cuts, cool at least 8 hours.
- When ready, lift the bars from the pan using the parchment overhang, transfer to a cutting board and slice with a sharp knife.