In a bowl, combine flour and salt; cut in shortening until the mixture resembles coarse crumbs. Combine 5 tablespoons water egg and vinegar; sprinkle over dry ingredients, 1 tablespoon at a time. Toss lightly with a fork until dough forms a ball; add additional water if necessary. Divide into two balls; chill while preparing filling.
In a saucepan, cook potatoes, carrots, celery and onion in water for 10 minutes or until crisp-tender; drain well. Add pork, gravy, rosemary if desired, salt and pepper; set aside.
On a floured surface, roll one ball of dough to fit a 9-in. pie plate. Fill with meat mixture. Roll remaining pastry to fit top of pie. Cut slits in top crust and place over filling; seal and flute edges. Brush pastry with cream if desired. Bake at 375° for 50-55 minutes or until golden brown. Yield: 6 servings.