Preheat your oven to 350°F (175°C). Line an 8×8-inch square baking pan with parchment paper, leaving an overhang on the sides. This makes it easy to lift the brownies out once they have cooled. Lightly grease the parchment with non-stick cooking spray.

In a large mixing bowl, combine the melted butter and granulated sugar. Whisk vigorously for about two minutes. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract. This step incorporates air, which helps create that desirable “crackly” top.

Sift the cocoa powder, all-purpose flour, and salt into the wet mixture. Use a spatula to gently fold the ingredients together until just combined. Do not overmix, as this can make the brownies tough. Fold in the chocolate chips at the very end.

In a small bowl, mix the creamy peanut butter with the powdered sugar until smooth. Spread half of the chocolate brownie batter into the prepared pan. Drop spoonfuls of the peanut butter mixture over the batter. Cover with the remaining brownie batter and use a knife to gently swirl the layers together for a marbled effect.

Place the pan in the center rack of the oven. Bake for 30 to 35 minutes. The center should be set but still slightly soft. Remove from the oven and immediately top with the red and green festive sprinkles. Allow the brownies to cool completely in the pan before lifting them out and slicing into squares.