Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt. In another bowl, cream softened butter with granulated and brown sugars until fluffy, then add the egg and vanilla extract. Gradually incorporate dry ingredients until combined.

In another bowl, combine flour, baking soda, and salt. Cream softened butter with remaining sugars until airy, add peanut butter, egg, and vanilla, then blend in dry ingredients.

Scoop equal portions of chocolate and peanut butter dough, roll together to create swirls.

Drop dough balls onto baking sheets, spacing them apart. Bake for 10-12 minutes.

Allow cookies to cool on sheets for 5 minutes before transferring to a wire rack.