Whisk together flour, cocoa, baking soda, baking powder and salt in a small bowl to aerate and combine; set aside.

Beat butter with electric mixer on medium-high speed in a large bowl until creamy. Add brown sugar and sugar and beat until lightened, about 3 minutes, scraping down bowl as needed. Beat in vanilla, then beat in eggs one at a time allowing each one to be incorporated before adding the next. Beat in the dry mixture until a few streaks of flour remain. Add chocolate chips and chopped peppermint candy and beat just until combined. Cover the bowl and chill for at least 4 hours but preferably overnight.

Position racks in upper and lower thirds of oven. Preheat oven to 350°F/180°C. Line two baking sheet pans with parchment paper. Form golf ball sized balls and place the cookies 8 per pan, spaced evenly apart. No need to press them down.

Bake for about 9 to 12 minutes or until lightly browned with the edges firmer than the centers, which should be soft. The cookies firm up tremendously upon cooling. Cool cookies still on pans placed on racks. Subsequent batches of dough should be placed on cooled pans. Store cooled cookies in airtight containers for up to 3 days.