Heat the oven to 400°F. Cut the stick of butter into chunks. Grease a baking sheet with more butter. Put all the ingredients in a food processor and pulse several times; as soon as the mixture resembles coarse meal, stop. Turn the dough onto a sheet of plastic, wrap it, and press it gently into a ball. Refrigerate the dough for at least 20 minutes or up to several hours.
Pinch off heaping tablespoon?sized pieces of the dough and roll them into 1?inch balls with your hands. Put the balls on the prepared pan, leaving 2 inches between them. Press down on each ball with your fingers to flatten it to ¾ inch thick. If there is dough left over when the sheet is filled, wait and cook a second batch.
Bake for 10 to 12 minutes, until the shortbreads are puffed and golden brown. When they're cool enough to handle, transfer them to a wire rack and bake the remaining dough. Serve right away or store covered at room temperature for up to 1 day.
My books include the bestselling How to Cook Everything and Vegan Before 6 P.M. (VB6), where I provide all the necessary tools for making the switch to a Flexitarian diet with lists for stocking the pantry, strategies for eating away from home in a variety of situations, pointers for making cooking on a daily basis both convenient and enjoyable, and a complete 28-day eating plan showing VB6 in action.