1. Sift together the flour, cocoa, ancho powder, cinnamon, salt, and pepper, then sift again. In a medium bowl, cream together the butter and the 10 tablespoons sugar until light. Mix in the vanilla, then add the flour mixture. Stir and knead the dough (it will be dry and crumbly at first) until it is smooth and supple.

2. Between 2 sheets of waxed paper, roll the dough out as evenly as possible to a thickness of ¼-inch. Chill for 30 minutes.

3. Meanwhile, position racks in the upper and lower thirds of the oven and preheat to 275°F. Lightly coat two cookie sheets with solid vegetable shortening.

4. Cut out the cookies with a 2-inch round cutter. Pierce each cookie twice with the tines of a fork. Spread the coating sugar on a small plate. Lightly press the top of each cookie into the sugar, so that the sugar clings to the dough. Arrange the cookies, sugar side-up, on the prepared sheets, spacing them about 1 inch apart.

5. Bake the cookies, exchanging the position of the sheets on the racks from top to bottom and from front to back, until the cookies are crisp and firm, about 40 minutes.

6. Remove from the oven and cool the cookies on the sheets on racks for 5 minutes. Transfer to paper towels and cool completely.

7. Store the cookies airtight at room temperature. They will be better the day after they are baked and will keep for about 1 week.