Preheat Oven:

Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.

Cream Butter and Sugars:

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

Add Peanut Butter and Eggs:

Mix in the peanut butter, eggs, and vanilla extract until fully combined.

Combine Dry Ingredients:

In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, mixing until just combined.

Prepare the Dough:

Scoop about 1 1/2 tablespoons of dough and flatten it slightly in your hand. Spoon about 1/2 teaspoon of marshmallow fluff into the center, then fold the dough around it, sealing it completely. Roll gently into a ball.

Arrange on Baking Sheet:

Place the dough balls about 2 inches apart on the prepared baking sheets.

Bake:

Bake for 10-12 minutes, or until the edges are set and the tops are slightly golden. The centers will still look soft, but they’ll firm up as the cookies cool.

Cool:

Allow the cookies to cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.