Combine all the ingredients in a food processor, and pulse until a smooth, stiff dough forms.
Wrap the dough in plastic and chill in the refrigerator for a few hours.
Preheat the oven to 350 degrees. Line two baking sheets with parchment paper.
Put the 1/4 cup sugar in a shallow bowl. Breaking off 1-tablespoon lumps, roll the dough into balls, drop into the sugar, roll to coat, and place 2 inches apart on the baking sheets.
Bake for 10 to 12 minutes, until the cookies are dark brown. Let cool on the baking sheets for a few minutes, then transfer to a rack to cool completely.