Recipe

Make Dough

1. Heat oven to 350°F. Line 2 large baking sheets with parchment paper.
2. In small heatproof bowl or glass measuring cup, combine chocolate, cocoa powder and espresso powder. In skillet or saucepan over medium-low heat, melt butter until bubbling but not browned, about 3 minutes, then pour over chocolate mixture. Without stirring, let mixture sit so butter’s residual heat melts chocolate thoroughly while you whip eggs and sugar.
3. In bowl of stand mixer fitted with whisk, add eggs, both sugars and kosher salt. (If using hand mixer, a large mixing bowl will do.) Whisk on medium-high speed until mixture is pillowy and sugars have begun to dissolve, 3 to 5 minutes.
4. Stir chocolate mixture until glossy and smooth. (If any solid pieces of chocolate remain, you can microwave in 10-second increments until everything is melted.)
5. With mixer on low speed, add vanilla and then chocolate mixture to egg mixture. Scrape sides and bottom of bowl to make sure chocolate is distributed evenly, then add flour and mix on low speed until only a few streaks of flour remain. To avoid overmixing, use a spatula to finish folding in flour. Dough should be glossy and resemble a very thick brownie batter.

Form and Bake Cookies

1. Using a 2-tablespoon scoop, scoop heaping amount of dough into mounds directly onto parchment-lined baking sheets, with portions at least 2″ apart, to make about 18 cookies. Work quickly to ensure cookies stay shiny once baked.
2. Bake for 8 minutes, or until cookies have started to spread and take on shiny outer surface, then remove pans from oven and whack on a heatproof counter a couple of times to give cookies cragged tops. (This also helps give cookies a fudgier consistency.)
3. Top with flaky sea salt and return to oven to finish baking for another 2 minutes, until shiny and slightly puffed. Cool for 2 minutes directly on baking sheets before transferring to wire rack to cool completely.