These peanut butter s’mores bars take the classic campfire treat and turn it into a chewy, chocolatey bar. A peanut butter–forward graham cookie dough forms the base and top, while a thick middle layer of milk chocolate, more peanut butter, and marshmallow fluff creates the gooey s’mores center. They’re simple to assemble and deliver the perfect peanut butter and s’mores combination.
This recipe is a peanut butter twist on classic s’mores and a sister recipe to the s’mores cookie bars. The dough is a chewy peanut butter cookie base with some flour replaced by graham crumbs to mimic graham crackers. The center layer is built with milk chocolate, a spread of peanut butter, and marshmallow fluff so you get that familiar s’mores texture without needing a campfire.
Making Peanut Butter S’mores Bars
Start by making the peanut butter graham cookie dough — no mixer required. Melt the butter and whisk it together with smooth peanut butter and brown sugar until smooth. Add the egg, an extra egg yolk, and vanilla, then stir in the flour and salt until the dough is lump-free. Fold in graham crumbs for that unmistakable s’mores flavor.
Assemble the bars as follows:
- Scoop out about 1 cup of the peanut butter graham cookie dough and set it aside for the topping.
- Press the remaining dough into the bottom of a lined 8×8 inch pan to form an even base layer.
- Place a layer of milk chocolate over the cookie dough and press it down gently — whole bars or broken pieces both work.
- Spoon and spread warmed smooth peanut butter over the chocolate. Microwave the peanut butter for 30–45 seconds on medium power and stir first to make spreading easier.
- Spread a layer of marshmallow fluff on top of the peanut butter. Warming the fluff briefly in the microwave (about 30 seconds on medium) makes it much easier to spread.
- Form the reserved cup of cookie dough into flat discs and place them over the marshmallow layer, covering as much of the marshmallow as possible. Some exposed marshmallow is fine — it will puff and create pockets of goo when baked. If fully covered, the marshmallow will remain more evenly distributed.
- Bake in a preheated 350°F (180°C) oven for about 30–35 minutes, or until the top is golden and the top cookie dough looks set.
Recipe Tip
Allow the bars to cool completely — ideally 8 hours — before cutting for the cleanest slices. Slicing while warm results in very gooey pieces that can fall apart; waiting yields neater bars. I cut some after four hours for photos and they were still gooey but held together without needing a spoon.
An Important Note About Marshmallow Fluff
Do not substitute regular marshmallows for marshmallow fluff (marshmallow creme). Regular marshmallows will melt into the dough during the extended bake, leaving no distinct marshmallow layer. Use marshmallow fluff to maintain the soft, gooey center.
More S’Mores Treats to Love
- Easy S’mores Bars – graham crust with a thick chocolate layer topped with marshmallows
- Golden Graham S’mores Bars
- S’mores Cookie Bars
Peanut Butter S’mores Bars
Equipment
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8×8 inch (20×20 cm) pan
Ingredients
Peanut Butter Graham Cookie Dough
- ½ cup unsalted butter (112 grams), melted
- ¼ cup smooth peanut butter (about 65 grams)
- ¾ cup brown sugar (158 grams) — light brown recommended
- 1 large egg
- 1 large egg yolk (in addition to the whole egg)
- 1 teaspoon vanilla extract
- 1½ cup all-purpose flour (188 grams)
- ¼ teaspoon salt
- ½ cup graham crumbs (about 50–60 grams — ~4–5 sheets)
Filling Ingredients
- 2 XL Hershey’s Milk Chocolate Bars (or 1½ cups chocolate chips)
- ½ cup smooth peanut butter (about 130 grams)
- 1¼ – 1½ cups marshmallow fluff (marshmallow creme)
Instructions
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Preheat the oven to 350°F (180°C). Line an 8×8 inch (20×20 cm) square pan with parchment paper, leaving an overhang for lifting the bars out later.
Make the Peanut Butter Graham Cookie Dough
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Whisk together melted butter, smooth peanut butter, and brown sugar until no lumps remain and the butter is incorporated.
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Whisk in the egg, additional yolk, and vanilla until combined.
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Stir in the flour and salt until the dough is smooth with no flour pockets, then stir in the graham crumbs.
Assemble & Bake
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Scoop out about 1 cup of dough and reserve for the top layer.
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Press the remaining dough into the prepared pan to form an even base.
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Layer chocolate on top of the base and press lightly so it adheres. Break bars as needed to cover the surface.
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Warm the peanut butter in a heatproof bowl for 30–45 seconds on medium power, stir until smooth, then spread over the chocolate layer.
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Warm the marshmallow fluff in a heatproof bowl for 30–45 seconds on medium power, then spoon and spread it over the peanut butter into an even layer.
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Form the reserved dough into flat discs and arrange them on top of the marshmallow layer, covering most of the surface but allowing a few small exposed areas.
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Bake for about 30–35 minutes in the center of the oven, until the top is golden and the dough looks set. Exposed marshmallow will puff up slightly.
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Cool completely in the pan. Use the parchment overhang to lift the bars onto a cutting board and slice with a sharp knife. Warm bars will be very gooey and may fall apart.
Notes
- Peanut Butter: Use smooth peanut butter that doesn’t separate; oil-separated peanut butter can affect texture.
- Marshmallow Fluff: This recipe requires marshmallow fluff (marshmallow creme). Regular marshmallows will melt into the dough and eliminate the marshmallow layer.
- Chocolate Bars: Bar sizes vary by country. If you want full coverage, use multiple bars or 1½ cups of chocolate chips.
- Nutrition: Values are an estimate per bar if the pan is cut into 12 equal slices.
- Storage: Store cooled bars in an airtight container at room temperature for up to 5 days.
Nutrition
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