In a large bowl, mix the flour, sugar and salt together. Cut in the shortening using a pastry blender or criss crossing 2 knives until dough is the size of small peas. Add the white vinegar and the egg. Mix with knives or a pastry knife until just combined. Sprinkle with cold water, 1 tablespoon at a time. Mixing with a fork until all of the flour is moistened. Gather the dough into a ball and wrap the ball in saran wrap and put in the fridge for 30 minutes. This will make the crust more firm and the dough flakier. This recipe makes two single pie shells or one top and bottom pie shell. Roll the dough onto a lightly floured surface, into a large circle. Fold dough in half and place half the circle into the pie shell.