Double-chocolate Cookies

Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper.

Melt 4 oz of the semisweet chocolate chips with the unsalted butter in a heatproof bowl over simmering water, stirring occasionally until smooth. Remove from heat and let cool slightly.

Whisk together the all-purpose flour, sifted cocoa powder, baking powder, and salt in a small bowl; set aside.

In a large bowl, whisk the egg and 3 egg whites together until combined. Add the packed brown sugar, vanilla extract, and brewed strong coffee, then whisk until well incorporated.

Stir the cooled chocolate mixture into the egg mixture until fully blended.

Fold the flour-cocoa mixture into the chocolate batter using a spatula until just combined; do not overmix.

Fold in the remaining 2 oz of semisweet chocolate chips.

Sprinkle the granulated sugar onto a shallow plate or dish. Drop spoonfuls of batter into the sugar, coating lightly on all sides, then place on the prepared baking sheets about 2 inches apart.

Bake for 12 minutes, or until the cookies are set but still slightly soft in the centers.

Remove from oven and let the cookies cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.