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

In a medium bowl, mix the flour, cocoa powder, baking soda, and salt for the chocolate dough.

In a larger bowl, cream the softened butter with granulated and brown sugars until light and fluffy.

Mix in the egg and vanilla extract, then fold in the dry ingredients until just combined.

For the peanut butter dough, whisk together flour, baking soda, and salt in a separate bowl.

Cream the butter with the sugars, add peanut butter, egg, and vanilla, and combine with the dry ingredients.

Take equal portions of each dough and roll them together to create swirls.

Place the dough balls on the baking sheets with enough space to expand.

Bake for 10-12 minutes, until the edges are set and the centers are slightly soft.

Cool on the baking sheets for 5 minutes before transferring to a wire rack.