Instructions

1. Preheat oven to 350°F. Grease and line a 9″x9″ glass pan with parchment paper. Set aside.
2. In a microwave-safe bowl, melt the butter. Remove from microwave, stir in sugar, and melt again for 30 seconds. Stir again and melt once more, this time for 60 seconds. You want the sugars and butter to bubble up slightly, but not burn. This amount of time should do the trick.
3. Remove mixture from microwave and stir in bittersweet chocolate. This should melt the chocolate completely. If it doesn’t, put it in the microwave for another 15 seconds. Allow to cool slightly before whisking the eggs and vanilla extract.
4. In a large bowl, mix the dry ingredients, then pour in the wet ingredients, mixing only until combined.
5. Pour batter into prepared pan.
6. Place the peanut butter in a microwave-safe bowl, and heat for 15 seconds. Stir in the butter and powdered sugar, then spoon over brownie batter in 12-16 dollops at random. Use a knife to mix the layers into a swirl pattern.
7. Bake for 40 minutes, or until a knife inserted in the center of the brownies comes out mostly clean (a little batter is fine, it will turn into delicious fudgyness). Allow to cool for 15 minutes before removing from pan and cutting into 9 large squares.