
"Real" shortbread is typically made with a little rice flour, which gives it that dry and delicate crunch. Instead of seeking rice flour, you can get an excellent result by using cornstarch to help achieve the classic texture. Sprinkle on a little green sanding sugar to celebrate "the day that's in it," as the Irish say.
The Irish often use self-rising flour for baking, although it's much less common in the US. If you're following a recipe from an Irish book or site that calls for self-rising flour, many American substitution charts will tell you to substitute 1 cup all-purpose flour plus 1 teaspoon baking powder. Do not do this! It's far too much baking powder and you'll end up with a cake or biscuits that taste like salty aluminum. A far better proportion is 1 teaspoon baking powder for every 2 cups of all-purpose flour.
