Line 2 baking sheets with parchment paper.

Melt the chocolate according to package directions; let cool.

In a medium bowl, whisk together the flour, cocoa, baking powder, and salt.

Using an electric mixer, beat the butter and brown sugar until light and fluffy, about 3 minutes. Beat in the eggs and vanilla, the cooled chocolate and 2-3 drops of mint extract.

Reduce the mixer speed to low and gradually add the flour mixture, mixing just until incorporated.

Place the powdered sugar in a small bowl. Drop a slightly heaping tablespoon of dough into the powdered sugar (the dough will be soft) and roll to coat and form into a ball; repeat with remaining dough. Chill for at least 30 minutes.

Heat oven to 350 degrees F. Lightly toss the chilled cookie dough balls in powdered sugar and arrange on the prepared baking sheets, spacing them 2" apart.

Bake, rotating the position of the pans halfway through, until the cookies are puffed, cracked, and just set around the edges: 9 to 11 minutes. Immediately sprinkle a bit of powdered sugar onto the cookies. Top with crushed candy cane. Let cool on the sheets for 3 minutes, then transfer to a wire rack to cool completely.