In 5-quart saucepot over high heat, heat unpeeled sweet potatoes and enough water to over to boiling. Reduce heat to low; cover and simmer until sweet potatoes are just fork-tender but not soft, about 20 minutes; drain. Cool sweet potatoes until easy to handle.
Meanwhile, slice onions 1/4 inch thick. In 12-inch skillet over medium-high heat, in hot vegetable oil, cook onions and 1/4 teaspoon salt until tender, stirring occasionally.
Preheat oven to 375°F. Grease 13" by 9" baking dish. Peel sweet potatoes and cut into 1/4-inch thick slices. In bottom of baking dish, arrange one-third of sweet potatoes; sprinkle with half of onions. Place half of remaining sweet potatoes over onion layer, then top with remaining onions.
Arrange remaining sweet potatoes over onions.
In 1-quart saucepan over medium heat, melt butter; stir in flour, ginger, pepper, and 1 teaspoon salt until blended; cook 1 minute.
Gradually stir in milk; cook, stirring constantly, until sauce boils and thickens slightly.
Pour sauce over potatoes in baking dish; sprinkle with parsley. Bake 30 minutes or until sauce is bubbly and mixture is heated through. If you like, broil 1 minute to brown top of potatoes slightly. Makes 6 accompaniment servings.
Serving Size: 6
