Chocolate Polvorones (Mexican Wedding Cookies)

Position racks in upper and lower thirds of oven; preheat to 325 degrees F. Line 2 rimmed baking sheets with parchment paper or baking mats.

Combine chocolate, all-purpose flour, pastry flour, granulated sugar and salt in a food processor. Pulse until the chocolate is broken into pieces ranging in size from very coarse sand to a generous 1/4 inch. Add butter, oil and vanilla. Pulse until the mixture begins to clump together. Transfer to a large bowl and mix and squeeze the dough to incorporate any remaining flour.

Using a scant 1 tablespoon each, shape the dough into 40 balls. Place 1 1/2 inches apart on the prepared baking sheets. Bake, rotating the pans from top to bottom and front to back halfway through, until the cookie tops look dry, show a few hairline cracks and do not feel squishy when lightly pressed with a finger, 20 to 22 minutes. Cool on the pans for 5 minutes, then transfer to a wire rack to cool completely.

Sift confectioners' sugar over the cookies. Grate cinnamon stick over the tops, if desired.