* Peel potatoes if desired. Saute garlic in melted margarine in a small saucepan until tender. Stir in cornstarch, salt and pepper. Add milk, stirring well. Cook over medium heat, stirring constantly, 2 minutes or until mixture is thickened and bubbly. Remove sauce from heat, and set aside. Arrange half each of potatoes, onion, and parsley in bottom of a 2 quart casserole dish coated with cooking spray. Top with half of sauce. Repeat layers with remaining potatoes, onion, parsley and sauce. Cover and bake at 350 degrees F. for 45 minutes. Stir once during baking time. Uncover and bake an additional 30 minutes or until potatoes are done.