In a large bowl, mix white sugar, brown sugar, peanut butter, softened butter, and egg.

Stir in all-purpose flour, baking soda, baking powder, and salt until well combined. Cover and refrigerate for 2 hours.

Preheat oven to 375°F. Shape dough into 1" balls and place on an ungreased cookie sheet. Flatten with a fork in crisscross patterns.

Bake for 8-9 minutes until lightly browned. Place a marshmallow in the center of each cookie and bake for another 2 minutes. Use a spatula to flatten the marshmallows.

Let cookies cool for 5 minutes on the cookie sheet, then transfer to a wire rack to cool completely.

Melt chocolate in a small bowl in 30-second increments. Swirl chocolate onto each cookie using a spoon.