Preheat the oven to 350. In a medium bowl, whisk together flour, cocoa powder, salt, and baking soda. In a large bowl, combine butter with both brown and granulated sugar until fluffy.
Add in the egg and vanilla extract, and mix until smooth. Add in the flour mixture, mix until it is fully combined. Roll the cookie dough into balls, and place one peanut butter cup on each piece of cookie dough.
Roll the cookies into a ball, covering the chocolate completely. Place the cookies onto a large ungreased baking sheet at least 2-inches apart. Bake for 10-12 minutes.
