In the bowl of a food processor, combine the almonds and icing sugar. Process for 1 minute. Add the chopped chocolate, 50 grams of sugar, the cocoa, cinnamon, and salt, and process together for another minute. Add the egg whites and the vanilla and pulse to form a dough.
Transfer dough to a parchment-lined surface, then knead it together to form a smooth disk. Let the dough sit for 10 minutes uncovered. Top with a second piece of parchment and roll out the dough to ¼ inch thickness.
Slide parchment onto a cutting board or sheet pan and chill cookie dough 10 to 20 minutes.
Preheat the oven to 325ºF and line two baking sheets with parchment. Cut out stars (with a 2-inch cookie cutter), and toss stars in granulated sugar before placing on baking sheet. Bake 1 sheet at a time for about 13 to 15 minutes. The stars will have crackled a little. Let cool before transferring to a wire rack. You can reroll dough scraps and cut out and bake more stars until you run out of dough.