Peanut butter filled chocolate cookies

Cookies:
1 1/2 cups all purpose flour
1/2 cup unsweetened cocoa powder
1/2 tsp baking soda
1/2 cup unsalted butter, softened
1/2 cup white sugar
1/2 cup brown sugar
1/4 cup peanut butter
1 tsp vanilla extract
1 egg


Filling:
1/3 cup peanut butter
1/2 cup powdered sugar
1 tsp vanilla extract


Preheat oven to 350 F. Line cookie sheets with parchment paper, or use non stick cookie sheets.
In a bowl, combine flour, cocoa powder, and baking soda. Set aside.
In another bowl, mix butter with white sugar until fluffy, add brown sugar.
Mix in peanut butter until well incorporated. Then add vanilla and egg. Blend well.
Using a spatula or a wooden spoon, gently mix in flour mixture.
Shape dough into 3/4inch balls and place on cookie sheets.

For peanut butter filling, mix powdered sugar, vanilla, and peanut butter (you can use a mixer)
and shape into 1/4inch balls. 
Flatten each chocolate dough ball and top with a peanut butter ball. Wrap chocolate dough over the peanut butter filling so that it completely covers the filling. Roll into balls again and flatten.
Bake for 8 minutes or until just set and surface is slightly cracked. Cool cookies for 1 minute before transferring them to wire racks to cool completely.