Preheat oven to 350 degrees F. Line a baking sheet with parchment paper or Silpat baking mat. Set aside.

In a medium bowl, whisk together flour, baking soda, salt, and cocoa. Set aside.

With a mixer, cream butter and sugars together until smooth. Add in eggs, one at a time. Next, add in vanilla and mix until combined.

Gradually add flour mixture and beat until flour disappears. Take a golf ball sized ball of dough, roll into a ball, and flatten it into a disc. Place a peppermint patty in the center and wrap the excess dough up and around the patty. Make sure the entire patty is covered. Repeat with remaining dough and place on prepared baking sheet, about 2 inches apart.

Bake cookies for 8-10 minutes, or until cookies are set, but still soft in the center. Remove from oven and let sit on baking sheet for 3 minutes. Move to a cooling rack and cool completely. Dust the cookies with powdered sugar.