In a 10-inch heavy skillet or 12-inch wok, heat the butter over moderate heat until a drop of cold water flicked into it splutters instantly. Add the mustard seeds and fry for 30 seconds. Thoroughly stir in the onions, ginger, salt and pepper, and drop in the green beans. Stirring constantly, add the red pepper and fry for 5 minutes longer. Add the coconut and coriander, reduce the heat to low, and cover the pan. Stirring occasionally, cook for 10 minutes more, or until the beans are tender. Sprinkle with lemon juice, taste for seasoning, and serve at once. Foods of the World: The Cooking of India Time-Life Books uploaded by Diane Lazarus