Peanut-Butter Swirl Brownies

INGREDIENTS

8 tbsp

unsalted butter, cut into small pieces, plus more for pan

2 oz

good-quality unsweetened chocolate, coarsely chopped

4 oz

good-quality semisweet chocolate, coarsely chopped

2/3 cup

all-purpose flour

1/2 tsp

baking powder

1/4 tsp

salt

3/4 cup

granulated sugar

large eggs

2 tsp

pure vanilla extract

4 tbsp

unsalted butter, melted

1/2 cup

confectioners' sugar

3/4 cup

smooth peanut butter

1/4 tsp

salt

1/2 tsp

pure vanilla extract