Roast vermicelli in a kadai with some salt till a little red in colour.
Add 2 tbsp of ghee to it. Roast for some more time.
Once it turns reddish in colour, add 3/4 cup of hot water. Mix it very well. (Note: water should be less than the vermicelli or it will become very soggy). Remove it from the gas after a minute. Keep aside in a flat plate.
In the same kadai, heat oil and add mustard seeds. Once they pop, add urud dal, chana dal, red chillies, curry leaves and mix well. When it's pale red, remove.
Add all the vegetables except tomatoes. Mix well.
Now add the green chillies, turmeric and salt and mix well.
Add the tomatoes and fry for 1 minute.
Then add water - the water should be just as much as the vegetables, not less. Cook for 2 minutes.
Now add the seviyan. Mix well and heat for a minute.