You'll need peanut butter, sugar, and a few other simple ingredients to make this easy recipe.
Cream together butter, sugar, and light brown sugar until smooth and creamy.
Mix in egg and vanilla extract with the hand mixer until just combined.
Mix in cornstarch, flour, and baking soda with a spoon or spatula.
Drop dough onto baking sheets, flatten into 3-inch disks, and add 1 tablespoon marshmallow fluff.
Form the dough around the marshmallow fluff and press peanut butter chips into the dough balls.
Bake the cookies for 9-10 minutes, then remove from oven to wire rack and allow to cool completely.
Serve with a tall glass of milk and enjoy!