• Preheat oven to 350F (175C) and line a 9x9” (22x22cm) baking pan with parchment paper. Set aside.
• In a microwave-safe bowl, combine butter and chocolate and heat in the microwave for 30 seconds. Stir well, and continue heating in 20 second increments until completely melted and smooth.
  8 Tablespoons unsalted butter, 4 oz semisweet chocolate bar
• Immediately add cocoa powder, whisk to combine.
  ½ cup natural cocoa powder
• In a separate large mixing bowl, use an electric mixer to vigorously beat together sugar, eggs, and vanilla extract until lightened in color/pale yellow (about 1 minute on medium/high speed).
  1 ½ cups granulated sugar, 3 large eggs, 1 teaspoon vanilla extract
• Drizzle the chocolate mixture into the egg mixture and stir until completely combined and batter is uniform.
• Sift flour and salt over the mixture and stir until flour is completely absorbed and batter is well-combined.
  ⅔ cup all-purpose flour, ½ teaspoon table salt
• Add chocolate chips (if using) and stir well.
  ½ cup mini chocolate chips

Assemble & Bake

• Measure out about 2 Tablespoons of peanut butter and set this aside for your topping.
  1 cup creamy peanut butter
• Spread half of the brownie batter evenly into the bottom of the pan. Dollop the remaining (larger amount of) peanut butter over the brownies and use the back of a spoon to gently smooth it almost all the way to the edges of the brownie batter (I like to leave about ¼-½” of space around the perimeter .
• Gently dollop the remaining brownie batter over the peanut butter and use the back of a spoon to gently nudge all the way to the edges of the pan so the peanut butter layer is completely covered. Dollop reserved peanut butter over top of brownies and use a knife to gently swirl into the brownies.
• Transfer to center rack of 350F (175C) preheated oven and bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
• Allow to cool completely before serving (they’re so messy to cut into when warm!).