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

In a medium bowl, whisk together the flour, baking soda, salt, and cocoa powder until well combined.

In a large mixing bowl, beat the softened butter with both sugars until light and fluffy, about 2-3 minutes on medium speed.

Mix in the egg and vanilla extract until fully incorporated.

Gradually add the dry ingredients to the wet mixture, mixing just until combined.

Using a tablespoon, drop dollops of cookie dough onto your baking sheet. Add small dollops of peanut butter on top and swirl using a toothpick or knife.

Bake in the preheated oven for 10-12 minutes, or until the edges are set but centers are still soft.

Allow to cool on the baking sheet for a few minutes before transferring them to wire racks to cool completely.