To make the cookies:

Cup of Yum
1. Preheat oven to 350°F and line a cookie sheet with parchment paper or silicone baking mat. Pour 1/2 cup of sugar into a small bowl and set aside.
2. Whisk together flour, baking soda, and salt in a mixing bowl and set aside.
3. Using a standing mixer or electric hand mixer, cream together butter, brown sugar and peanut butter.
4. Add the egg and vanilla and continue mixing.
5. Gradually pour bowl of dry ingredients into the wet ingredients and mix just until combined.
6. Divide dough into small balls, about 1 inch in diameter each.
7. Form each ball into a log shape, then roll in sugar.
8. Place logs on cookie sheet about 2 inches apart.
9. Using the tines of a fork, make a criss-cross pattern in your dough logs, then pinch the middle of the cookie to make a peanut shape.
10. Bake 10-12 minutes, until lightly browned on the edges, but still soft in center.
11. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.

To make the peanut butter filling.

1. Using a standing mixer, beat butter on medium speed until fluffy.
2. Mix in peanut butter, 1 cup powdered sugar, milk and vanilla extract.
3. Gradually mix in the remaining powdered sugar until smooth.
4. Group your baked cookies into pairs, then spoon 1 Tablespoon of filling on the bottom cookie for each pair.
5. Place a second cookie onto the top of the filling to create a sandwich.