Decadent Peanut Butter Marshmallow Brownies Recipe

Why You Will Love This Recipe

• Gooey and fudgy: A dense, fudgy brownie base topped with melty marshmallows for the ultimate texture contrast.
• Peanut butter and chocolate: A classic pairing—the rich, nutty peanut butter balances the chocolate for deep, comforting flavor.
• Quick and approachable: Despite the layered appearance, the steps are straightforward and the bake time is short.

Ingredient Notes

Full ingredient amounts appear in the recipe card below. A few notes to help you choose the best versions for these brownies:

1. Step 1: Preheat the oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper and lightly spray or grease it.
2. Step 2: In a medium bowl whisk melted butter, granulated sugar, room-temperature eggs and vanilla until the mixture is lighter in color and slightly fluffy.

3. Step 3: Whisk together salt, all-purpose flour and 3 tablespoons cocoa powder in a separate bowl. Fold the dry ingredients into the wet mixture just until combined; do not overmix.
4. Step 4: Spread the batter evenly into the prepared pan and sprinkle with chocolate chips.

5. Step 5: Bake for about 17–20 minutes, or until the edges are set and a toothpick inserted near the center comes out with a few moist crumbs. The center should remain fudgy.

6. Step 6: As soon as the brownies come out of the oven, warm the peanut butter briefly (about 10–20 seconds) until pourable. Spread the warm peanut butter evenly over the hot brownies.

7. Step 7: Scatter mini marshmallows over the peanut butter layer and return the pan to the oven for 3–5 minutes, until the marshmallows puff and begin to soften and brown lightly.

8. Step 8: While the marshmallows start to cool slightly, make the chocolate frosting: melt butter with 2 tablespoons cocoa powder and the milk until hot enough to dissolve the cocoa. In a bowl combine powdered sugar and salt, then stir in the hot chocolate mixture and beat until smooth. Add vanilla, mix, and spread the frosting over the warm marshmallow layer. Let the brownies cool fully so the frosting sets before slicing.

Expert Baking Tips

• Swap nut butters freely: creamy peanut butter or other nut butters will work if you prefer a smoother top layer.
• Measure flour by weight when possible; grams produce more consistent results. If you don’t have a scale, spoon flour into your measuring cup and level it—avoid packing.
• Watch the oven closely during the final bake. You want the brownies set at the edges but still soft in the center for the best fudgy texture.

Yes. If you double the ingredients, bake the batter in a 13×9-inch pan and add a few extra minutes to the bake time, checking for doneness.

Yes. Substitute a 1:1 gluten-free all-purpose flour blend and follow the same method; results are usually excellent.

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Ingredients

• ½ cup (113.5 g) salted butter, melted
• 1 cup (200 g) granulated sugar
• 2 large eggs, room temperature
• 1 teaspoon vanilla extract
• ½ teaspoon salt
• 3 tablespoons cocoa powder (for batter)
• ¾ cup (100 g) all-purpose flour
• ¼ cup (45 g) chocolate chips
• ½ cup (129 g) peanut butter (crunchy or creamy)
• 2 cups (about 100 g) mini marshmallows
• ¼ cup (56.75 g) butter (for frosting)
• 2 tablespoons cocoa powder (for frosting)
• ¼ cup (59 ml) milk
• 2 cups (240 g) powdered sugar
• ¼ teaspoon salt (for frosting)
• ½ teaspoon vanilla (for frosting)

Instructions

1. Preheat oven to 350°F (175°C). Line an 8×8-inch pan with parchment and grease it.
2. Whisk melted butter, sugar, eggs and vanilla until combined and slightly aerated.
3. Mix salt, flour and 3 tablespoons cocoa powder separately, then fold into the wet ingredients until just combined.
4. Spoon batter into the pan, smooth the top, and sprinkle chocolate chips over the surface.
5. Bake 17–20 minutes until the edges are set and the center is still fudgy. Remove from oven.
6. Warm peanut butter briefly until pourable, spread over hot brownies, then top with mini marshmallows. Return to the oven 3–5 minutes until marshmallows puff.
7. Make the frosting by melting ¼ cup butter with 2 tablespoons cocoa and ¼ cup milk until hot. Combine powdered sugar and ¼ teaspoon salt in a bowl, add the hot butter mixture and beat until glossy. Stir in ½ teaspoon vanilla.
8. Spread frosting over the warm marshmallow layer. Cool completely so the frosting sets before slicing into squares.

Notes

You can use any nut butter in place of peanut butter. If you prefer a less textured top, choose creamy peanut butter. For best consistency when baking, measure flour by weight if possible. If not, spoon and level the flour into the cup measure to avoid packing.

Nutrition (per serving)

Calories: 403 kcal • Carbohydrates: 56 g • Protein: 5 g • Fat: 19 g