Pennsylvania Sweet Potatoes in Tangy Sauce Recipe

Place sweet potatoes in a large kettle and add water to cover. Cook over medium heat until barely tender; drain. Peel and cut potatoes into fourths. Arrange in a medium size casserole. Preheat oven to 350F. While potatoes are cooking, combine sugars, ginger and cornstarch in a small saucepan. Add pineapple juice and lemon juice. Stir over medium heat until sugars are dissolved and mixture starts to bubble; stir in margarine. Pour sauce over potatoes. Bake uncovered 50 to 60 min or until sauce is thickened.