Prepare and bake Graham Cracker Piecrust in a 9-inch pie plate, and cool on a wire rack.
Preheat oven to 350°.
To prepare filling, combine the sweet potato and the next 7 ingredients (sweet potato through eggs) in a food processor; process until smooth. Scrape sides of bowl once. Pour mixture into prepared crust.
To prepare streusel, place hazelnuts on a baking sheet. Bake at 350° for 15 minutes, stirring once. Turn nuts out onto a towel. Roll up towel; rub off skins. Chop nuts. Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, brown sugar, and cinnamon in a bowl; cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal. Stir in hazelnuts. Sprinkle filling with streusel. Bake pie at 350° for 45 minutes or until set. Cool on a wire rack.