Preheat oven to 400 degrees. In a large saucepan, cover the sweet potato slices with water and bring to a boil. Reduce heat to moderate and cook until just tender. About 5 minutes. Drain well.
Arrange potato slices in a large casserole. Season with salt and pepper and then dot with butter pieces. Drizzle potatoes with maple syrup, sprinkle with water and bake for 25 minutes or until tender and lightly browned. If necessary, you can broil the casserole for a minute or two before serving.