Preparation

1. Lightly coat a 9-inch square baking pan with nonstick cooking spray and line with parchment paper. Reserve.2. Put the butter and both chocolates into a heatproof bowl and place over a pot of simmering water. Once the butter/chocolate mixture is almost completely melted, stir in cocoa powder and espresso powder. Set aside to cool to room temperature.3. Using a hand mixer, beat the eggs to break them up, then gradually add the sugar. Mix until light and thickened, about 1 to 2 minutes. Add vanilla extract and beat until well combined.4. Stir the flour and salt into the chocolate mixture until just incorporated. Fold the chocolate mixture into the egg mixture until the batter is no longer streaky; reserve.5. Prepare the peanut butter swirl by combining the peanut butter, confectioners’ sugar and melted butter and stirring until combined. 6. Pour the batter into prepared pan. Dollop the peanut butter mixture on top and, using a fork or knife, decoratively swirl into the batter. Transfer pan to oven. 7. Set oven to Bake at 350ºFfor 20 minutes, or until edges are just dry. Cool completely and chill in the refrigerator overnight before cutting and serving.