Add water and salt to cleaned tapioca. The water level should be 2-3 inches higher than tapioca. Bring to a boil and reduce the flame to the lowest.
Cook till the tapioca is done. Drain the excess water. Mash the tapioca well.
Combine coconut, small onion, green chili, garlic, jeera, curry leaves and turmeric powder using your finger tips.
Make a well in the center of the mashed tapioca and add coconut mixture. Cover it with tapioca. Cover and cook it for 5-7 minutes on low flame. Mix it well. You can drizzle some coconut oil at this stage, if you like.
Heat oil in a pan and crackle the mustard. Add sliced onion and curry leaves. When onions turn light golden, add coconut and fry it, till it becomes golden brown. Add this to the cooked tapioca and mix well.