1 c. unsalted butter (room temperature)
3/4 c. superfine sugar
1 1/2 c. all-purpose flour
1/2 c. cornstarch
1 tsp. vanilla (optional)
1/4 tsp. salt

Preheat oven to 325 degrees and have 8 or 9 inch cake or pie pan ready. Cream butter with sugar until smooth, beat in vanilla. Sift the flour with the cornstarch and salt and add to butter mixture. Beat until well blended, taking care not to overwork dough. Flour hands lightly and pat dough into pan. Prick dough all over with fork. With knife divide dough into 8 wedges, without cutting all the way through. Score outside edges of shortbread dough with the tines of a fork. Bake 40-50 minutes until pale golden brown. Cool shortbread in pan 20 minutes. Turn shortbread out onto a rack to complete cooling. Cut in wedges to serve.