Preheat your oven to 350°F (175°C).
In a large mixing bowl, cream together the softened butter, peanut butter, granulated sugar, and brown sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition, then stir in the marshmallow fluff.
In another bowl, whisk together the flour, baking soda, and salt. Gradually mix the dry ingredients into the wet ingredients until just combined.
Fold in the chocolate chips until evenly incorporated.
Scoop tablespoon-sized portions of the dough onto a lined baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes or until the edges are lightly browned but the centers remain soft.
Remove from the oven and allow to cool on the baking sheet for a few minutes before transferring to a wire rack.