For the Pie Crust, mix flour, granulated sugar and salt in large bowl. Cut in butter with pastry blender or 2 knives until mixture resembles pea-size crumbs. Add ice water, a tablespoon at a time, tossing dough with fork after each addition. Add enough water so that dough comes together. Gather dough into a ball. Roll dough on lightly floured surface to a 12-inch circle, about 1/8-inch thick. Carefully place pie crust on rolling pin and transfer to 9-inch deep dish pie plate. Gently press the pie crust onto bottom and up sides of pan. Trim pie crust so that it extends 1/2-inch beyond edge of pie plate. Fold under excess pie crust. Flute the edges of the pie crust or press with tines of a fork. Refrigerate until ready to fill.
Preheat oven to 350°F. For the Sweet Potato Filling, pierce sweet potatoes with a fork. Place on foil-lined baking pan. Bake 1 hour or until fork tender. Increase oven temperature to 425°F. Cool sweet potatoes slightly. Halve sweet potatoes. Scoop out flesh into large bowl. Mash with potato masher until smooth. Add remaining ingredients; mix well. Pour into prepared crust.
Bake 15 minutes. Reduce oven temperature to 350°F. Bake 35 to 40 minutes longer or until a knife inserted near center comes out clean. Cool completely on wire rack.
Preheat oven to 400°F. For the Marshmallow Meringue, mix marshmallow creme and vanilla in large bowl. Set aside. Place egg whites, cream of tartar and salt in mixer bowl. Beat on medium speed with whisk attachment until well blended. Add granulated sugar, 1 tablespoon at a time, beating on high speed 2 to 3 minutes or until shiny stiff peaks form. Gently stir 1/2 of the egg white mixture into marshmallow cream until well blended. Gently stir in remaining egg white mixture. Spread meringue evenly over sweet potato filling, forming decorative peaks with spatula.
Bake 4 minutes or until meringue is lightly browned. Serve immediately.