Place the onions in a pan and fill it with water and cook until it is tender
Remove the center of the onions with a sharp knife.
Dry roast the vermicelli until golden in color.
Heat oil in a pan and toss in the curry leaves, mustard, onion trimming and chillies. Cook until the onions are tender.
Add turmeric powder, salt and vermicelli. Add water and simmer until the water is absorbed.
Stir in the remaining ingredients. Place the filling inside the onion shells.
Serve hot with spicy tomato chutney.