In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugars together on medium high speed until pale and creamy, about 3 minutes. Add the eggs one at a time, mixing after each. Add the vanilla extract.

In a separate bowl, stir together the flour, cocoa powder, cinnamon, cayenne pepper and salt. Add to the mixer and mix until combined. Stir in the chopped chili chocolate. The dough will be very thick.

Roll into rounded tablespoons and roll in the coarse sugar, if desired. Place on the prepared sheet and press down on the rounds so that they have a flat top. Bake until tops are cracked and edges are set, 8-10 minutes. Let cool on the sheet pan for 5 minutes, then transfer to a wire rack to cool completely.

Store the cookies in an air-tight container at room temperature for up to 5 days.