Add the flour, cocoa powder, salt, baking soda, and baking powder into a medium bowl and mix until just combined.
Beat the butter and both sugars in a mixer on medium speed until fluffy and light in color — about 4 minutes.
Beat in the egg until well-combined, at least another 1-2 minutes. Then beat in the vanilla.
Stir in the flour mixture and beat on low until just combined.
Stir in a cup of the peppermint chunks. Fold until evenly distributed.
Create 1-tablespoon balls of cookie dough and then stick more peppermint chunks onto the balls of dough.
Place the cookie dough on a baking sheet and chill for an hour. Preheat the oven to 350F.
Divide the cookie dough balls on parchment or silicone baking mat-lined baking sheets at least 2-inches apart.
Bake one baking sheet at a time for 10 - 12 minutes, or until the edges are set and the centers are puffy and not too raw looking.
Remove from the oven and allow to cool on the baking sheet for at least 3 minutes before transferring to a wire rack to cool completely.
Notes
You can freeze unbaked cookie dough balls until ready to bake. Add another minute to the baking time. Store cookies in a room temperature airtight container for up to a week.