Whisk together the flour, cocoa powder, espresso powder, baking powder, salt and baking soda in a small bowl.
Melt the chocolate and butter in a medium microwave-safe bowl in the microwave in1-minute increments, stirring in between, until smooth. Let cool slightly.
Beat the brown sugar and eggs with an electric mixer on medium-high speed in a large bowl until thick, about 2minutes. Scrape the chocolate mixture into the egg mixture and beat until incorporated. Add the flour mixture and beat until just combined.
Refrigerate the dough until it is firm – at least 2 hours or overnight.
Position oven racks in the top and bottom thirds of the oven and preheat to 350°F. Line2 baking sheets with parchment paper.
Put the confectioners' sugar in a small bowl. Scoop out tablespoonfuls of the dough and roll them into balls. Refrigerate half the dough balls. Toss the remaining balls in the sugar, coating them very generously (you shouldn't see any dough peeking through). Arrange the balls about1 inch apart on the prepared baking sheets.
Bake until the cookies spread, the tops are dull in color and cracked and the edges are firm, 12 to 14 minutes. Let cool on the baking sheets for a few minutes, then transfer to a wire rack to cool completely. When the baking sheets are cool, repeat with the remaining dough balls.