Take oil in Kadhai add mustard seeds hing and let it crackle then add chopped onions green chilli and cook well. Once cooked add the chopped veggies with salt to taste and cook well. Now it time to add the milk leaving 2 tablespoons for slurry. Add the milk let it boil then add a slurry of corn flour mixed with a pinch of salt and 2 tablespoons of milk let there be no lumps. Add this mixture to the veggies and boil till it becomes thick. Serve with dosa or roti.