Mix sugars, peanut butter, butter, and egg in a large bowl. Stir in remaining ingredients. Cover and refrigerate for 2 hours.
Preheat your oven to 375 F. Shape dough into 1" balls (about a teaspoon). Place on an ungreased cookie sheet. Flatten in crisscross patterns with a fork.
Bake 8-9 minutes until just light brown. Place a marshmallow into the center of each cookie and bake for another 2 minutes. Remove from oven and use a spatula to flatten the marshmallows.
Let cool for 5 minutes, then remove from cookie sheet and cool on a wire rack.
Melt the chocolate in a small bowl in 30 second increments. Using a spoon, swirl chocolate onto each cookie.