Swirly Peanut Butter Brownies

Adapted from the America's Test Kitchen Family Baking Book

8 tbsp (1 stick) unsalted butter
3 oz. unsweetened chocolate, chopped coarse
2/3 cup all-purpose flour
1/2 tsp baking powder
1/4 tsp salt
1 cup sugar
2 large eggs, lightly beaten
1 tsp vanilla extract
1/3 cup chunky peanut butter

1. Place an oven rack in the middle position. Preheat to 350 F. Line an 8-inch square baking pan with a foil sling (2 pieces of foil crossed over each other and smoothed down) and grease the foil. Melth the butter and chocolate together in the microwave, stirring often, 1-3 minutes. Let the mixture cool slightly.

2. In a small bowl, whisk together the flour, baking powder, and salt. In a medium bowl, whisk together the sugar, eggs, and vanilla. Whisk in the melted chocolate mixture until just combined. Stir in the flour mixture until just incorporated.

3. Scrape the batter into the prepared pan. Plop the peanut butter evenly around the top of the batter. Run a butter knife through the batter to create swirls.

4. Bake brownies 22-27 minutes. Let cool completely on a wire rack, about 2 hours. Remove from pan using the foil, cut into squares, and enjoy!