Thaw potatoes for 30 minutes. Press between paper towels to remove moisture. Set aside.
In a 10-inch ovenproof skillet cook onion, apple, sage, and water over medium heat until onion is tender. Remove from heat. Stir in potatoes and ham.
Combine milk, egg product or eggs, cheese, and salt. Pour egg mixture into skillet. Do not stir. Bake, uncovered, in a 350 degree F oven for 30 to 35 minutes or until center appears just set. Garnish with fresh sage, if desired. Makes 6 servings.