Cut 4 pieces of aluminum foil, each 30 cm by 30 cm. Place one salmon fillet in the middle of each sheet of foil. Top each salmon with a mixture of chestnuts, carrots, onions, ginger, and lemongrass. Sprinkle with soy sauce, sesame oil, and cilantro. Top with butter, fold the pockets and bake for dozen minutes in a 350 degree oven. Cut the pockets open and serve immediately.