In a large bowl, whisk together flour, baking soda, baking powder & salt. Cut in white & yellow shortening until it resembles small peas. In a one cup measure, place egg & vinegar; combine. Add enough cold water to make 3/4 cup. Pour all at once over flour mixture, mixing quickly, until dough pulls away from sides of bowl. This should only take a couple of minutes; DO NOT OVERMIX PASTRY. Cover with plastic wrap & place in refrigerator until filling is ready.