Coarsely chop the prawns and mix with the ginger, garlic, lime peel and palm sugar. Chill for at least 3 hours. Fry the mixture in a hot pan until the prawns turn pink. Remove from heat. Mix together the sweet chilli sauce and chicken stock, and simmer to thicken. Stir into the prawn mixture. Soften a sheet of rice paper in warm water. Place on a board, top with 4 spinach leaves and 2T (30ml) prawn mixture. Fold in the top and bottom, and roll to enclose the filling. Repeat with remaining ingredients. Serve with soy sauce and lime wedges.