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

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

Cream butter, brown sugar, and granulated sugar until light and fluffy.

Mix in egg, vanilla extract, and milk until smooth.

Gradually combine dry ingredients with wet ingredients to form a thick dough. Fold in chocolate chips.

In another bowl, stir together peanut butter, powdered sugar, melted butter, and vanilla extract.

Scoop cookie dough onto prepared baking sheets. Add spoonfuls of peanut butter mixture and swirl gently with a toothpick.

Bake for 10–12 minutes until edges are set and centers remain soft.

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