Step 1

Heat the oven to 350 degrees. Line two baking sheets with parchment paper.

Step 2

Melt the butter in a small pot over medium heat, swirling, until it's starting to foam and brown, 3 to 4 minutes. (Whisk the butter from time to time so that the solids don’t stick to the bottom of the pot.) Let cool.

Step 3

Whisk the confectioners’ sugar, cocoa powder and salt in a medium bowl, ridding it of as many lumps as possible. (If you really want to, feel free to sift everything.)

Step 4

Using a spatula, mix in the egg whites, whole egg and browned butter, stirring until you’ve got a good, smoothish mixture (any small lumps will take care of themselves), followed by the chocolate and any nuts you may want to add.

Step 5

Using a spoon, drop quarter-size blobs of dough (the texture is really somewhere between a dough and a batter) onto the baking sheet, spacing them about 2 inches apart (they spread a lot). Sprinkle with flaky salt and bake until the cookies have flattened considerably and look baked through and a little wrinkled, 6 to 8 minutes. Let cool before eating so they can firm up.