Scoop the batter into balls then flatten them in your hand & add about 5 mini marshmallows then pinch the dough to seal & roll the dough in your hands.
Roll the cookie dough ball in the sugar. Place the cookie dough balls on a parchment-lined baking sheet or plastic container and chill in the fridge for 30 minutes.
Bake for 9 minutes then quickly take the sheet out of the oven and bang it on the counter to encourage the cookie to spread and the marshmallow to explode out.