·       In a medium bowl, whisk together flour, baking soda, and salt.

·       In a stand mixer fitted with a paddle attachment, combine butter, peanut butter and brown sugar and beat on medium speed until light an fluffy.

·       Add egg and vanilla and beat to combine.

·       Add dry mixture and beat again to combine until you have a thick dough.

·       Cover the bowl with plastic wrap and place in the fridge for at least 30 minutes, preferably up to 1 hour.

·       Preheat oven to 325 °F. Prepare two baking sheets with nonstick silicon mats or parchment paper and set aside.

·       Grab a medium cookie scoop and fill it halfway with dough, pressing it into the bottom and up the sides. Spoon a teaspoon of marshmallow fluff into the center, and then top with more dough to fill the scoop. Place each ball of dough on prepared baking sheets, with no more than 6 on each, evenly spaced out with plenty of room for the cookies to spread.

·       Bake for 9-11 minutes until the cookies have spread and started to crinkle on top. Remove from the oven and let cookies cool for at least 15 minutes on the baking sheet itself – they will continue to spread and set a bit more as they cool. Carefully move to wire racks to cool completely. Enjoy!