I wanted to experiment a little and I turned my favorite peanut butter cookies into fluffernutters by adding a half of a marshmallow to the tops of the cookies! It worked so well.
Preheat the oven to 350 degrees. Line a baking sheet with parchment paper.
In the bowl of a stand mixer, cream together the butter, peanut butter, and sugars until light and fluffy. Beat in the egg. Stir in the vanilla.
In a medium bowl, combine the flour, baking soda, and salt. Gradually add to the creamed mixture and beat until well combined.
Use a medium cookie scoop to drop balls of dough on the cookie sheet, leaving at least 1 inch between each cookie. Use your hands to gently flatten the dough a bit.
Bake for 4 minutes and remove from the oven. Carefully top each of the cookies with the halved marshmallows and return to the oven for 4 more minutes.
Let the cookies set on the baking sheet for 5 minutes to set up before transferring to a wire cooling rack.