For the pie
Peel the sweet potatoes and pick with a fork. Lightly oil them and place on a rack in a baking pan. Bake the potatoes at 180⁰C until very tender, about 35 minutes. Cool. Mash the sweet potatoes until completely smooth. Combine with the remaining ingredients, blending well. Pour into the prebaked pie shell and bake at 180⁰C until the filling is set, about 35 minutes. Cool completely, and then refrigerate until the filling is completely set before serving. You may serve with whipped cream and roasted walnuts or hazelnuts.