Shortbread Cookies

Preheat oven to 325 degrees. Cream butter and sugar together. Sift in flour and cornstarch and blend together using a pastry cutter until the ingredients all come together. (If mixture seems excessively dry, cut in 1 more tablespoon of butter—but only if you really need it.) Form dough into a big ball, wrap in plastic wrap, and refrigerate 20 minutes. Roll onto a lightly floured surface and cut into rounds. Place on a cookie sheet lined with parchment paper or a baking mat. Bake for 20 minutes. Do not allow shortbread to brown; the edges should have the faintest golden tinge. Check your oven sooner if it runs hot.