Irish Shortbread Cookies Ingredients 1 cup salted butter 2⁄3 cup sugar 1⁄2 cup cornstarch 2 cups flour Beat butter until creamy. Sift sugar and cornstarch into bowl. Sift flour into mixture. Beat until crumbly. Pat into ball. Spread into ungreased 10x7 pan. Bake at 275 for 30 minutes. Reduce oven to 250 bake a90 minutes longer. Sprinkle with powdered sugar. Cut into bars. Share with friends.