Combine the flour, sugar, and salt in a large mixing bowl/ food processor . Add the butter and toss gently with your hands, to coat with flour. If you are using bowl then use your pastry blender, cut the butter into the flour to break it up partially. Large, random-size pieces of butter will remain. If using food processor then pulse few minutes.

Continue to cut both fats into the flour the flour has a meal-like consistency. All the flour should look as if it has been "touched" by the fat, and small, split pea-size pieces of fat should remain.

To this add sourdough starter, then add vinegar and over the mixture. If using food processor pulse few seconds . Then when the dough pulls together.

Using a pastry fork or other large fork, quickly stir the mixture with a few strokes, "lifting" the mixture up from the bottom of the bowl as you stir. Gently pack the dough into a ball.

Place the dough on a long sheet of plastic wrap and dust it lightly with flour. Flatten the dough into a 10-inch disk slightly less than ¾" thick. Wrap in the plastic, place this inside a plastic bag, and refrigerate for at least 1 to 2 hours before rolling. Makes a single crust for a 9" - 9½" standard or deep-dish pie.