Heat oven to 325° and position rack to middle position.
Chop unsweetened chocolate and add to a microwave safe bowl. Add butter and microwave in 20 second intervals stirring after each, until chocolate is melted. Allow to cool. Whisk together brown sugar, eggs, vanilla, and espresso powder together in a large bowl. (Instant coffee can be substituted for espresso powder.) Add the chocolate and butter mixture and stir to combine.
Whisk flour, Dutch process cocoa powder, baking soda and salt together in a bowl. Fold flour mixture into wet ingredients until there are no dry streaks. Allow the dough to sit for 10 minutes.
For 4 dozen small cookies, scoop dough into one tablespoon portions using a tablespoon or a 1 tablespoon scoop. For 2 dozen large cookies, portion dough using a 2 tablespoon scoop. Drop cookies (unrolled) directly into granulated sugar and roll around to coat, then roll into a ball. Next, roll the sugar coated ball into the powdered sugar and place on a parchment lined cookie sheet… one dozen cookies per sheet.
Bake one sheet at a time for 8-9 minutes for small cookies, 10-12 minutes for large cookies. Cookies will puff up and crackle and will be soft in the center. Allow cookies to cool on the sheet pans.
These cookies are still delicious with natural cocoa powder, light brown sugar, and without the addition of espresso powder...but they are deeply chocolatey and deliciously complex as written. Totally enjoyable either way!! This recipe is slightly adapted from ATK’s Chocolate Crinkle Cookies.