Chop the vegetables into 2-inch pieces. Dice the potatoes accordingly. On medium flame, boil the vegetables with green chillies, curry leaves, salt and turmeric powder with some enough water. The vegetables should be tender but crunchy.
Grind the coconut and the masalas.
Beat the curd and mix well.
Add this curd mixture to the boiled vegetables and cook for few more minutes until the masalas are well absorbed in the vegetables.
Heat oil in a small pan, add cumin seeds, mustard seeds, red chillies and curry leaves.
Once the seeds crackle, add this tempering to the vegetables.
Before serving, add about 2 tbsp of coconut oil on the top without heating.
Serve with fried papad or accompanied by rice and sambar.