Instructions

1. Preheat oven to 350°F. Line a 9 x 9-inch square baking pan with parchment paper on all sides. 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 the 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 adding the eggs and vanilla extract. Whisking until smooth and frothy.
4. Add the flour, cocoa powder and salt to the wet ingredients, and mix until just combined and no streaks of flour remain.
5. Scrape the batter into prepared pan and smooth into an even layer.
6. Place the peanut butter in a microwave-safe bowl, and heat for 15 seconds. Stir in the butter and powdered sugar and mix until smooth. Drop spoonfuls of the peanut butter mixture all over the top of the brownies batter. 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). Allow to cool for 15 minutes before removing from the pan and cutting into 9 large brownies or 16 small brownies!