In a mixing bowl, stir together flour, cornstarch, and the ¼ sugar. Rub in butter with your fingers until mixture is very crumbly and no large particles remain. With your hands, gather mixture into a ball; place in an ungreased 8 or 9-inch round baking pan with a removable bottom, or in a 9-inch spring-form pan. Firmly press out dough into an even layer.
With the tines of a fork, make impressions around edge of dough; then prick surface evenly. Bake in a 325 degree oven for about 40 minutes or until pale golden brown. Remove from oven and, while hot, cut with a sharp knife into 8 to 12 wedges. Sprinkle with about 1 tablespoon sugar. Let cool completely; then remove sides of pan and lift out cookies. Store airtight. Makes 8 to 12.