Heat 1 cup gravy or sauce; pour over egg and mix well. Add onion and turkey. Season to taste. Prepare biscuit dough with milk, as for biscuits. Roll dough into rectangle about 1/4-inch thick. Spread turkey mixture on dough, leaving 1 inch clear at far long side. Roll gently toward far side. Place seam side down on ungreased cookie sheet, and bake 25 minutes or until golden and cooked. Heat remaining gravy to serve with roll slices.