Measure out all ingredients and chop the bittersweet chocolate into small ½-inch pieces—this size matters because smaller pieces melt smoothly and distribute evenly throughout the dough. Brew your espresso and let it cool to room temperature while you work; this prevents the eggs from cooking when combined later. Combine the flour, baking powder, and salt in a bowl, whisking them together to distribute the leavening evenly. This prevents lumps and ensures consistent rise in your cookies.

Set up a double boiler by placing a heatproof bowl over a pot of simmering water, making sure the bowl doesn't touch the water. Add the chopped chocolate and melted butter to the bowl, stirring occasionally until completely melted and smooth. Once melted, remove from heat and let cool for about 5 minutes—you want it warm but not hot, so it doesn't cook the eggs when combined.

In a separate bowl, whisk together the room-temperature eggs, cooled espresso, and sugar until the mixture is smooth and slightly pale, about 1-2 minutes of whisking. The eggs need to be at room temperature so they incorporate smoothly without scrambling when you add the warm chocolate. I like to use room-temperature eggs because they blend more evenly and create a better texture in the final cookie.

Pour the cooled chocolate mixture from Step 2 into the egg mixture from Step 3, stirring until fully incorporated. Add the dry ingredient mixture from Step 1 and fold gently until just combined—don't overmix, as this develops gluten and makes cookies tough. The dough should be dark, rich, and slightly thick. Cover the bowl and refrigerate for 2-3 hours until the dough is firm enough to scoop and roll without sticking to your hands.

About 15 minutes before the dough finishes chilling, preheat your oven to 350°F and line your baking sheets with parchment paper. Place the confectioners' sugar in a shallow bowl and have it ready near your workspace. This prep work means you can move directly from shaping to baking without any delays.

Working with the chilled dough from Step 4, scoop tablespoon-sized portions and roll them between your palms into smooth balls. Working quickly keeps the dough from warming up too much. Roll each ball generously in the confectioners' sugar from Step 5 until fully coated—this sugar creates the signature crackled finish as the cookies bake and spread. I like to do this just before baking so the sugar coating stays white and prominent rather than absorbing moisture from the dough.

Place the sugar-coated dough balls 2 inches apart on your prepared baking sheets. Bake at 350°F for about 10 minutes—the cookies should look slightly underbaked in the center, as they continue to set while cooling. Remove from the oven and let them rest on the baking sheet for 5 minutes to firm up slightly, then transfer them to a wire cooling rack to cool completely. This resting period prevents them from breaking apart when you move them.