Cream butter in a mixing bowl; gradually add sugar, beating well. Add potatoes; beat at medium speed of electric mixer until well blended. Add eggs, one at a time, beating well after each addition. Place brandy in a small pan; heat just until warm. Add brandy, lemon rind, juice, vanilla and nnutmeg to sweet potato mixture; stir until well blended. Pour mixture into a pastry shell. Bake at 180ºC for 40 minutes, or until a knife inserted in center comes out clean. Sprinkle pie with citron; cool immediately. Nutritional info per serving: 388 cal; 5g pro, 55g carb, 15g fat (35%)