Preheat your oven to 350°F (175°C). Line two large baking sheets with parchment paper.
In a medium microwave-safe bowl, combine the chopped chocolate and butter. Microwave in 20-second intervals, stirring well after each, until the mixture is melted and smooth. Set aside to cool for a few minutes.
In a large bowl using a hand mixer or in a stand mixer with the whisk attachment, beat the eggs, brown sugar, and granulated sugar on high speed. Continue for 3 to 4 minutes, until the mixture is pale, thick, and ribbon-like.
Reduce the mixer speed to low. Slowly pour in the slightly cooled chocolate-butter mixture, mixing until just incorporated. Add the vanilla and peppermint extracts and mix briefly.
Add the flour, cocoa powder, salt, and espresso powder to the bowl. Mix on low speed only until the dry ingredients are just combined and no flour streaks remain. Do not overmix.
The batter will be soft. Working quickly, use a 1.5-tablespoon cookie scoop to drop mounds of batter onto the prepared baking sheets, spacing them about 2 inches apart.
Bake for 10 to 12 minutes. The cookies should have crackly tops and set edges, but the centers will still be soft.
Remove the baking sheets from the oven. Immediately sprinkle the crushed peppermint candies over the hot cookies.
Let the cookies cool on the baking sheets for 5 minutes before transferring them to a wire rack to cool completely.