Step 1

Place two racks in the upper and lower thirds of the oven and preheat the oven to 375°F. Line 2 baking sheets with parchment paper.

Step 2

Break the almond paste into small pieces and place in the bowl of a food processor. Add the sugar, cocoa powder, and salt, and process until the almond paste is very finely chopped and incorporated with the salt and sugar. Add the egg whites and vanilla, and process until a smooth dough forms, about 30 seconds. Using a small scoop or spoon, dollop 1 tablespoon of the batter for each cookie onto the baking sheet, leaving 2 inches between each cookie. Top each cookie with a few almond slivers and sprinkle with sanding sugar.

Step 3

Bake the cookies for 13 to 14 minutes, rotating the baking sheets halfway through baking, until the cookies have risen and cracked slightly but are still soft in the center. Allow the cookies to cool completely on the baking sheets. Store the cookies in an airtight container.