Preheat the oven to 350°F (175°C).

Cream together the unsalted butter, granulated sugar, and brown sugar in a mixing bowl until light and fluffy.

Add the egg and vanilla extract, mixing until well combined.

Whisk together the flour, baking soda, salt, and cocoa powder in a separate bowl.

Gradually mix the dry ingredients into the wet mixture until just combined.

Fold in the peanut butter and chocolate chips until swirls form.

Drop tablespoon-sized portions of dough onto a lined baking sheet, spacing them apart.

Sprinkle a pinch of sea salt flakes on top of each mound.

Bake for 12 minutes or until edges are set and golden brown.

Cool on the baking sheet for a few minutes before transferring to a wire rack.