Bring sweet potatoes and water to cover to a boil in a large Dutch oven over high heat. Reduce heat, and cook 30 to 45 minutes or just until potatoes are tender. Drain and let cool to touch; peel. Cut ends off, and discard. Cut remaining potato into 1-inch-thick rounds. Arrange slices evenly into 12 stacks in a lightly greased 13- x 9-inch baking dish. Sprinkle evenly with chopped pecans.
Combine butter and next 6 ingredients; pour evenly over potatoes.
Bake at 350° for 25 minutes or until thoroughly heated. Garnish, if desired.