How to Make It
Peel potatoes, and cut into 1/8-inch-thick slices; set aside.
Melt butter in a skillet; add onion, and saute until tender. Remove onion from skillet, reserving drippings.
Sprinkle sweet potatoes with 1 tablespoon salt. Cook in batches in skillet until browned and almost tender, turning once. Place potatoes in a greased 13- x 9-inch baking dish.
Combine whipping cream, egg yolks, and eggs in a large bowl; stir in 2 teaspoons salt and next 7 ingredients. Pour over potatoes. Place dish in a shallow roasting pan; add hot water to pan to depth of 1 inch.
Bake at 350° for 45 minutes. Remove dish from water; cool. Chill 8 hours.
Remove from dish, and cut into desired shapes. Place on a lightly greased baking sheet.
Bake at 400° for 12 minutes or until thoroughly heated.
*A pinch of ground nutmeg and 1/4 teaspoon ground cinnamon may be substituted.