1. For the pastry, combine flour, sugar, 1/4 teaspoon cinnamon, 1/4 teaspoon nutmeg and pinch salt in a large bowl. With a pastry blender or 2 knives, cut in shortening until mixture resembles coarse crumbs. Gradually add orange juice, tossing with a fork, just until pastry holds together. Shape into a ball; flatten into a thick disk. Wrap well in plastic wrap and refrigerate 1 hour or overnight.
2. For the filling, whisk together eggs, sugar, mashed sweet potatoes, milk, butter, 1 teaspoon cinnamon, 1/2 teaspoon nutmeg, 1/4 teaspoon salt and cardamom in a large bowl.
3. Heat oven to 425 degree F. On lightly floured surface, roll pastry into a 12-inch circle. Fit into a 9-inch pie plate, leaving a 1-inch overhang. Flute edge. Pour in filling. Bake 10 minutes. Reduce oven temperature to 300 degree F. Bake 25 minutes. Cover edge loosely with foil. Bake 25 minutes more or until a knife inserted in center of filling comes out clean. Cool completely on wire rack. Serve with whipped cream, if desired. Makes 8 servings.