In a mixing bowl, beat creamy peanut butter, softened butter, and brown sugar together until light and fluffy. Add egg and vanilla extract, mixing until incorporated. In a separate bowl, whisk together flour, baking soda, and salt before gradually combining with wet ingredients.

In another bowl, whisk melted butter with white sugar until smooth. Stir in cocoa powder, egg, and vanilla extract. Gently fold in flour, baking powder, salt, and chocolate chips until the brownie dough is just combined.

Cover both doughs with plastic wrap or store in airtight containers and refrigerate for 30 minutes.

Preheat oven to 350°F (175°C). On a parchment-lined baking sheet, scoop both doughs, overlapping slightly. Use a toothpick to swirl them together.

Bake for 9-11 minutes until tops are crackly and edges are set.

Let cookies cool on baking sheet for 5-10 minutes before transferring to a wire rack.