Heat ghee in a pan or kadhai. Add mustard seeds and let it splutter
Add bay leaf, curry leaves, cumin seeds, urad dal and fry for a few seconds
Add onion and fry until it is translucent
Add tomatoes and fry until it is soft
Add the ground paste and saute for few minutes (until the raw smell of the masala disappears)
Add the vegetables, salt, and some water
Check for seasoning and bring to a boil
Simmer for 10-15 minutes until the vegetables are completely done and the saagu thickens slightly
Serve hot with poori, roti or dosa