vegetarian
gluten freePreheat the oven
Heat the oven to 350° F and line 1 to 2 baking sheets with parchment paper. Give yourself a little space to work, because this batter comes together quickly once you start mixing.
Whisk the dry ingredients
In a large bowl, whisk together the powdered sugar, cocoa powder, salt, and instant coffee until the mixture is evenly combined and you do not see any stubborn cocoa lumps. Breaking up the dry clumps here makes the finished cookies much smoother and more glossy.
Make the batter
Add the egg whites and the vanilla bean paste if using, then whisk until you have a thick, shiny batter that looks like brownie batter and slowly ribbons off the whisk. Keep mixing until everything is fully incorporated, about 2 to 3 minutes; the batter should be smooth, glossy, and thick enough to hold a scoop without running flat immediately.
Fold in the chips
Switch to a spatula and fold in the semi-sweet chocolate chips until they are evenly distributed. Try not to overwork the batter; just fold until the chips are tucked throughout.
Scoop the cookies
Scoop the batter into 12 mounds on the prepared baking sheet, spacing them about 2 inches apart so they have room to spread. If you want neater cookies, lightly smooth any rough peaks on top with the back of a spoon or a fingertip.
Bake until crackly
Bake the cookies until the tops are shiny and crackled, the edges look set, and the centers still look slightly soft, 10 to 12 minutes. They may seem a little underdone in the middle, but that is what keeps them fudgy once they cool.
Cool and serve
Let the cookies cool on the baking sheet for 10 minutes so they can finish setting, then transfer them to a rack or serve them slightly warm if you love a gooier center. Once cooled, the tops stay delicately crisp while the middles turn chewy and fudgy.
