1. Preheat oven to 375 degrees.
2. In a large bowl, whisk together flour, baking soda, and salt. Set aside.
3. In a large bowl using an electric mixer, cream together butter, peanut butter, and sugars. Add vanilla extract; stir until well combined.
4. One at a time, beat in each egg until well combined.
5. Slowly add four mixture to wet ingredients, mix until well combined.
6. Scoop dough into 1 inch balls, or use a disher to scoop balls of dough which I highly recommend. I can't believe I ever lived without a disher.
7. Place on ungreased cookie sheet or parchment paper lined cookie sheet. Flatten the balls with a fork.
8. Bake for 5-7 minutes, do not overtake. Cookies will set as they cool.
9. Cool cookies on cookie sheet for 3 minutes; transfer to a wire rack to cool completely.

Frosting Filling

1. In a large bowl using an electric mixer, cream together peanut butter, powdered sugar, vanilla extract, and milk until well combined.
2. Spread the peanut butter filling on half of the cookies and top each one with another cookie.