Heat oven to 425 degrees. Prepare piecrust according to package directions for filled one-crust pie using 9-inch pie pan. Flute edges to stand 1/2 inch above rim, or use braided edge. Boil sweet potatoes in small amount of water until soft when tested with fork; drain. Peel; mash. Measure 1 1/2 cups of mashed sweet potatoes into large bowl. Whisk in remaining ingredients; blend well. Pour filling into pastry-lined pie pan. Bake at 425 degrees for 10 minutes. Reduce heat to 350 degrees and bake an additional 50 to 60 minutes, or until filling is set and knife inserted in center comes out clean. Cover edge of crust with strips of foil after 30 minutes to prevent excessive browning. Cool. Makes 8 servings. NOTE: 1 1/2 cups of canned pumpkin can be substituted for sweet potaotes; omit nutmeg and add 2 teaspoons pumpkin-pie spice.