Chocolate Mudpie Cookies
4 cups confectioner's (powdered) sugar
1/2 cup plus 3 tablespoons unsweetened cocoa powder
1/2 teaspoon sea salt
4 large egg whites, room temperature
1 tablespoon vanilla
Preheat oven to 325F and position racks in the top and bottom third. Line your sheet pans with silpats. Or you can bake in batches with fewer pans.
Make sure your walnuts have cooled a bit, then chop coarsely and set aside. Sift together the confectioner's sugar, cocoa powder, and sea salt. Stir in the walnuts, then add the egg whites and vanilla. Stir until well combined.
Spoon the batter onto the prepared sheets in mounds of about 2 tablespoons each, allowing for plenty of room between cookies. Don't try to get more than 6 cookies on each sheet, and try to avoid placing the batter too close to the edge of the pan.
Bake until they puff up. The tops should get glossy, and then crack a bit - about 12 -15 minutes. Slide the cookies still on silpat onto a cooling rack, and let them cool completely. They will keep in an airtight for a couple days.