Chocolate cookies: Mix flour, cocoa powder, baking soda, and salt in a bowl. In a separate bowl mix butter and sugars until well creamed together. Mix in egg and vanilla extract. Mix in dry ingredients until combined.

Refrigerate dough for 30 minutes.

Preheat oven to 350 degrees F. Line baking sheets with parchment paper.

Roll dough into small, 2 teaspoon sized balls (about 30 cookies). Press down lightly on the top of the balls to slightly flatten.

Bake for 6-8 minutes. Cool 5 minutes on baking sheet, then remove to cooling rack to cool completely before frosting.

Peppermint frosting: Mix butter and cream cheese until smooth. Add powdered sugar and peppermint extract and mix for 2-3 minutes.

Assemble: Add small spoonful of filling onto inside of cooled cookie. Sandwich with another cookie, pressing gently until frosting peeks through. Dip outsides of cookie in crushed candy canes.