Firstly, rinse the moong dal a couple of times in water. Then soak the moong dal for 4 to 6 hours or overnight in enough water. Drain all the water in the morning.
Now grind it into a smooth paste with the green chilly, ginger, coriander leaves, salt with some water (add water as required). Add the rice flour and stir well. Heat up a pan and add some oil or ghee. With a big spoon, pour the dosa batter on the pan and use the same spoon for spreading the moong dal dosa batter into a round shape. Sprinkle finely chopped onions, green chilies and coriander leaves (optional). Now drizzle oil at the sides and in the center. Flip the dosa a couple of times until both sides are well cooked and browned. Your dosa is now ready to eat, you can enjoy your dosa with some coconut chutney.