Remove meat from bones and discard skin. Pour chestnut powder into small baking pan (an 20 cm aluminum pan works well; powder should be half to 1 cm deep). Press meat into powder. Cover and steam 30 minutes, or until powder has gelatinized into thick, heavy crust. Remove from steamer and let cool. Cover and chill until ready to complete. About 30 minutes before serving time, prepare sweet and sour plum sauce; set aside and keep warm. Warm a serving platter in low oven. Preheat oil in deep fryer to 190ºC . Slice duck into bite-size chunks and fry quickly in batches until crisp and browned. Remove with slotted spoon and drain on paper towels. Repeat until cooking is completed. Serve immediately with sweet and sour plum sauce topped with nuts. From Bon Appetit's "Oriental Favorites."