Maple Meringue Sweet Potato Casserole

Heat oven to 400 degrees F. Bake sweet potatoes on a foil-lined baking sheet 1 hour or until tender. Let cool to touch and peel. Reduce oven temperature to 350 degrees F. Beat sweet potatoes, 1 teaspoon vanilla, and next 6 ingredients at medium speed with a heavy-duty electric stand mixer until smooth. Beat in whole eggs. Spoon potato mixture into a greased 13- x 9-inch baking dish. Bake at 350 degrees F for 30 minutes. Meanwhile, beat egg whites, remaining 1/2 teaspoon vanilla, and a pinch of salt at high speed with a heavy-duty electric stand mixer until foamy. Gradually add maple syrup, beating until stiff peaks form. Beat one-third of marshmallow crème into egg white mixture; repeat with remaining marshmallow crème, beating until smooth (about 1 minute). Pipe or spread meringue in a decorative pattern on warm potatoes. Bake 13 to 15 more minutes or until meringue is lightly browned.