1. Preheat the oven to 350 degrees. Spray two baking sheet with cooking spray and set aside.
2. In a medium bowl, mix the peanut butter and sugars together until creamy and smooth. I do this by hand.
3. Add in the egg and vanilla extract. Mix until well combined.
4. Add the salt and baking soda. Stir until mixed together.
5. Spoon dough into balls, about 1 Tablespoon of dough for each cookie. Place the cookie dough balls on the greased baking sheets, about two inches apart.
6. With your thumb, press down the dough ball to make a puddle in the middle of each cookie. Bake for 10-12 minutes. Remove baking sheets from the oven. Press down the cookies with your thumb again. Do this quickly because the cookies will be hot. Let the cookies cool on the cookie sheet for two minutes.
7. Move cookies to a wire rack and cool. Once cool, take a spoonful of marshmallow cream and fill the center of the peanut butter cookies. The marshmallow creme will be sticky, but try to smooth it out as best as you can. Fill all of the cookies and serve.