Preheat your oven to 325°F (165°C). Line two large baking sheets with parchment paper.
Place the chopped chocolate and butter in a microwave-safe bowl. Microwave in 30-second bursts, stirring in between, until fully melted and smooth. Set it aside to cool down for a few minutes.
In a medium bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt.
In a large bowl, whisk the granulated sugar, brown sugar, eggs, and peppermint extract until combined. Whisk in the slightly cooled chocolate mixture until smooth.
Add the flour mixture to the wet ingredients and fold with a spatula until just a few streaks of flour remain. Fold in the crushed peppermint candies. Let the dough rest at room temperature for 10 minutes to firm up.
Place the extra granulated sugar and powdered sugar into two separate shallow bowls.
Use a 1.5-tablespoon cookie scoop to portion the dough. Roll each ball first in the granulated sugar to coat it completely, then roll it generously in the powdered sugar.
Place the dough balls about 2 inches apart on the prepared baking sheets.
Bake for 14 to 15 minutes, until the edges are set and the centers are puffed with cracks. Let the cookies cool on the baking sheets for 10 minutes before transferring them to a wire rack to cool completely.