Preheat oven to 350 degrees and line a cookie sheet with parchment paper

In a small bowl, mix together flour, baking soda, and salt; set aside.

Using a standing mixer, cream together butter, brown sugar and peanut butter.

Mix in the egg and vanilla until combined.

Gradually mix in the dry ingredients until just blended.

Form dough into 1 inch balls.

Shape into a log and roll log in sugar.

Place logs on cookie sheet about 2 inches apart.

Using the tines of a fork, make a criss-cross pattern in the dough.

Pinch the middle of the cookie to make a peanut shape.

Bake 10-12 minutes, until lightly browned on the edges and still soft in center.

Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.

Using a standing mixer, beat butter on medium speed until fluffy.

Beat in peanut butter, 1 cup powdered sugar, the milk and vanilla.

Gradually beat in remaining powdered sugar until smooth.

Pair up cookies to their respective size partners

Spoon 1 tablespoon of filling onto the bottom cookie

Place the top cookie onto the top of the filling and create a sandwich

Enjoy