In a large skillet cook sausage over campfire or medium heat until brown. Remove from skillet. Drain, reserving 1 tablespoon of pan drippings (add oil if necessary). In reserved drippings cook onion over medium heat about 4 minutes or until tender. Stir in cooked sausage.
Meanwhile, beat together eggs, milk, salt, mustard, and pepper. Pour over sausage mixture. Cook, uncovered, over medium heat without stirring until mixture begins to set on bottom and around edge. Using a metal spatula, lift and fold partially cooked egg mixture so uncooked portion flows underneath. Continue cooking about 4 minutes or until eggs are cooked throughout but still moist. Stir in apple. Sprinkle with snipped parsley. Serve immediately. Makes 4 servings.