Peanut Butter Swirl Brownies

Preparation

1. Step 1

   Preheat oven to 325°F. Butter an 8-inch square baking pan and line with parchment, allowing a 2-inch overhang. Butter lining (not overhang).

   Step 2

   Make batter: Put butter and chocolates in a heatproof medium bowl set over a pan of simmering water; stir until melted. Let cool slightly. Whisk together flour, baking powder, and salt in a bowl.

   Step 3

   Whisk granulated sugar into chocolate mixture. Add eggs, and whisk until mixture is smooth. Stir in vanilla. Add flour mixture; stir until well combined.

   Step 4

   Make filling: Stir together butter, confectioners’ sugar, peanut butter, salt, and vanilla in a bowl until smooth.

   Step 5

   Pour one-third of batter into prepared pan; spread evenly with a rubber spatula. Drop dollops of peanut butter filling (about 1 tablespoon each) on top of batter, spacing about 1 inch apart. Drizzle remaining batter on top, and gently spread to fill pan. Drop dollops of remaining peanut butter mixture on top. Gently swirl peanut butter filling into batter with a butter knife, running the knife lengthwise and crosswise through layers.

   Step 6

   Bake until a cake tester inserted into brownies (avoid center and edges) comes out with a few crumbs but is not wet, about 45 minutes. Let cool slightly in pan, about 15 minutes. Lift out; let cool completely on a wire rack before cutting into squares. Brownies can be stored in an airtight container at room temperature up to 3 days.

2. HOW TO MARBLEIZE BROWNIES

   Step 7

   Use two large spoons to drop dollops of filling over a base of chocolate batter. Add more batter on top, then more dollops of filling. Drag a butter knife back and forth with the tip touching the bottom of the pan.