Grate the coconut and in a mixer, take the coconut along with green chilies, ginger, and salt. Pulse it a couple of times, then add little required water to get a smooth paste.
Transfer this paste to a bowl, add all purpose flour to this mixture. Slowly add water and mix to get a batter without any lump.
Season it with cooking oil, mustard seeds, and curry leaves.
Heat a tawa and pour a ladleful of batter as you do with regular dosa batter and spread out. Sprinkle cooking oil and cook on both sides.