Ingredients
- 1 1/3 cups (167.3 g) regular unsweetened cocoa powder
- 1 cup (125 g) all-purpose flour
- 1 teaspoon baking powder
- 1/2 teaspoon kosher salt
- 1 teaspoon espresso powder
- 1 cup (2 sticks / 227 g) unsalted butter, room temperature
- 2 cups (400 g) granulated sugar
- 1 cup (168 g) semi-sweet chocolate chips
- 1 tablespoon vanilla extract
- 4 large eggs, room temperature
- 3/4 cup (193.5 g) creamy peanut butter
- 1 cup (96 g) marshmallow fluff
Pan: 9×13‑inch ceramic baking dish, lined with parchment.
Ingredient notes
- Cocoa powder + chocolate chips: Cocoa gives strong chocolate flavor and keeps the batter thick and fudgy, while chocolate chips melted into the hot butter–sugar mixture add extra richness and a shinier top.
- Espresso powder: A small amount of espresso powder boosts chocolate flavor without making the brownies taste like coffee.
- Butter + cooked sugar: Heating butter and sugar together, then cooling slightly before adding eggs, helps create a glossy, dense brownie with a crackly top.
- Peanut butter: Use regular creamy peanut butter (not natural) for the smoothest texture and most stable swirl or layer.
- Marshmallow fluff: Fluff melts and re‑sets into gooey pockets and streaks; using it in the center layer keeps it from burning on top.
Step‑by‑step instructions
Step 1: Prep the pan and oven
Preheat the oven to 350°F (175°C). Line a 9×13‑inch ceramic baking dish with parchment paper, leaving some overhang on the long sides to lift the brownies out easily. This helps prevent sticking and makes slicing cleaner.
Step 2: Mix the dry ingredients
In a large mixing bowl, whisk together the cocoa powder, flour, baking powder, kosher salt, and espresso powder until well combined and lump‑free. Sifting the dry ingredients first will give a smoother, more even batter, especially with cocoa.
Step 3: Cook the butter and sugar
In a medium saucepan, add the unsalted butter and granulated sugar. Melt over medium heat, stirring occasionally, until the mixture is fully melted, glossy, and reaches about 230°F (110°C). This step dissolves the sugar and helps create that shiny top and fudgy texture.
Remove the saucepan from the heat. Immediately stir in the semi‑sweet chocolate chips and vanilla extract until the chocolate is completely melted and the mixture is smooth. Let this mixture cool for about 10 minutes so it doesn’t scramble the eggs.
Step 4: Add the eggs
Once the chocolate mixture has cooled slightly, beat in the eggs one at a time, stirring constantly after each addition until fully incorporated. The mixture should become thick, glossy, and homogenous. Adding the eggs gradually helps prevent curdling and keeps the batter smooth.
Step 5: Combine wet and dry ingredients
Pour the chocolate mixture into the bowl with the dry ingredients. Using a spatula or whisk, fold together until just combined and no dry streaks of flour remain. Avoid over‑mixing; stop once the batter is uniform to keep the brownies tender and fudgy instead of cakey.
Step 6: Layer the batter, peanut butter, and fluff
Spread about half of the brownie batter evenly into the prepared 9×13 baking dish, smoothing it into the corners with a spatula.
Gently spread or dollop the creamy peanut butter over this first layer. If your peanut butter is very thick, you can warm it slightly in the microwave to make it easier to spread without tearing the brownie base. Then dollop the marshmallow fluff over the peanut butter layer in spoonfuls; using a piping bag makes distribution more even and helps avoid mixing the layers too much.
Carefully spread the remaining brownie batter over the marshmallow and peanut butter, doing your best to cover the filling. It’s okay if some peanut butter or fluff peeks through; the layers will settle as they bake.
Step 7: Bake
Bake in the preheated 350°F (175°C) oven for about 28–30 minutes, or until the edges are set and a toothpick inserted near the center comes out mostly clean, with a few moist crumbs but no wet batter. Because of the peanut butter and marshmallow center, the very middle may look slightly softer; avoid over‑baking if you want a fudgy texture.
Step 8: Cool and slice
Remove the pan from the oven and place it on a wire rack. Let the brownies cool completely in the pan so the layers can set; this may take 1–2 hours. Once cool, use the parchment overhang to lift the brownie slab onto a cutting board and slice into squares with a sharp knife, wiping the blade between cuts for the cleanest layers.