Combine dry ingredients. In a large mixing bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
Cream butter and sugar. In a large mixing bowl with an electric mixer, cream together the butter and sugar on medium-high speed, until light and fluffy, about 2 minutes. Scrape down the bowl as needed.
Add egg and vanilla. Add eggs, one at a time, beating until combined. Add in vanilla extract and mint extract. Beat to combine.
Add dry ingredients. Gradually add the dry ingredients, beating just until combined. You want to make sure to not overmix. With a wooden spoon, or spatula, stir in candies and chocolate chips. Cover and refrigerate dough for at least one hour, up to overnight.
Prep pan and ovens. Position a rack in the center of your oven and preheat the oven to 350°F (177°C). Line a baking sheet with parchment paper and set aside.
Scoop cookies. When ready to bake, allow the dough to sit at room temperature for several mintues to allow for easy scooping. Using a 1-inch cookie scoop, scoop dough and roll in your hands to form a smooth ball of dough and place on the cookie sheet, spaced about 2 inches apart.
Bake the cookies. Bake in a preheated 350°F oven on the middle rack, for 10-12 minutes until edges are set and middles are puffy but dry. Remove from the oven and let cool on the sheet for 5 minutes, then transfer to a wire rack to cool completely.