Grind all the ingredients for masala to a fine paste. Heat butter in a kadai and fry the finely sliced onion to a golden brown. Add ground masala paste and fry well. Mix in finely chopped tomato, green peas and the sliced mushrooms. Add about 1 1/2 cups of water. Add salt to taste. Allow to simmer on a slow fire till done. Sprinkle the chopped green coriander on the top and serve hot with chapatis, rotis or puris.