Preheat the oven to 350°F (175°C).

In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.

Add in the eggs and vanilla extract, mixing until well combined.

In a separate bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry mixture to the wet ingredients, mixing until just combined.

Fold in the creamy peanut butter until the dough is fully incorporated.

Scoop tablespoon-sized amounts of dough onto a lined baking sheet, spacing them about 2 inches apart.

Make a small indentation in the center of each dough scoop and fill each with marshmallow fluff.

Bake for 10-12 minutes, or until the edges are lightly golden.

Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack.