To prepare the stuffing - Heat oil in a pan and temper with cumin seeds and asafoetida. Saute for a few seconds. Add the onion and garlic.
Fry till light brown in colour. Now add the chopped spinach, salt, turmeric powder, chili flakes and coriander powder. Fry till the water is absorbed and spinach is well cooked. Keep aside to cool.
To prepare the stuffed dosa - Heat a tawa / griddle. Smear some oil and then sprinkle some water. After it sizzles off, wipe dry with a tissue water. This ensures a non-stick effect.
Pour a ladleful of the batter and spread it around into a circle with the back of the ladle. Add some oil over it and around the edges.
Add some of the spinach stuffing lengthwise and then when one side of the dosa is done, carefully roll it like a swiss roll and transfer to a serving plate.
Prepare similar stuffed dosas with the remaining batter and stuffing. Serve them with sambar and coconut chutney.
