In a large bowl, whisk the flour with the sugar and salt. Using a pastry blender, cut in the butter until the mixture resembles coarse meal. In a small bowl, whisk the egg with the egg yolk, then whisk in the water. Drizzle the egg over the flour mixture, and stir with a fork to lightly blend the ingredients. Squeeze gently until a smooth dough forms. Divide it in half, pat each half into a disk and wrap in plastic. Refrigerate until firm, about 1 hour.