Wash mung beans. Place with turmeric & ginger in a large pot. Add 4 cups water & bring to a boil, stirring often. Reduce heat to medium & simmer, partially covered, for 30 minutes. Turn off heat & beat with a wire whisk. When ready to serve, heat puree till piping hot. Stir in the lemon juice & salt. Heat ghee over a high heat in small frying pan. When very hot, carefully add the mustard seeds & fry till they start to turn grey. When they stop sputtering, add the chili. Stir rapidly for a monent & then turn off the heat. Pour over the puree & fold in the chopped coriander. This dal is excellent with almost every vegetable. Julie Sahni, "Classic Indian Cooking"