Three Grain Butter Pastry Recipe

Put the cornmeal and rolled oats into a blender and pulse the machine on and off until the oat flakes are reduced to small flecks; a few remaining larger pieces are fine(if you'r using oat flour, skip this first step). Transfer to a large mixing bowl and stir in the flour, sugar, and salt. Add the butter and cut it into the dry ingredients until the mixture resembles a coarse, damp meal, with the largest pieces about the size of split peas. Beat the egg yolk with 3 tablespoons of the cold water. Sprinkle this liquid over the dry mixture, working the mixture with a fork; push on it with the tines to help pack it. If the mixture is still dry, add another tablespoon of water, this time packing the dough with your hands. Pack it with some authority--you'll be surprised how it coheres when you do. If the dough still seems dry, add more cold water in dribbles. Stop adding cold water when the dough pulls together in a dampish but not tacky-wet ball. Divide the dough in half, then flatten each half into a disk about 1/2-inch thick; flatten it with your palm, right onto a piece of plastic wrap. Wrap the dough in the plastic wrap and refrigerate for at least 30 minutes before rolling.