Put refined oil in a deep vessel. Once hot, shallow fry gram flour until golden brown. Do this on a very low flame for about 15 minutes. Add the fenugreek seeds just as it starts to change colour.
Once it is golden brown, add turmeric powder and after a few seconds add all the water to it. With the water add cubed potatoes as they take longest to cook; let it all come to a boil. Then reduce the flame to medium.
Purée the tomatoes and add to the vessel. Let the kadhi simmer away on a low flame for an hour.
In the meanwhile, heat water in another small pot. Chop drum sticks into three-inch pieces and lotus stem into one-inch pieces. Parboil these and keep them aside.
Also, heat the oil for frying after parboiling is done. Deep fry cauliflower florets, colocasia and okra till golden brown. While frying add some salt to the veggies.
After the kadhi has simmered for an hour, add parboiled lotus stem and drum sticks to it. After another 10 minutes add the fried cauliflower, colocasia and okra together.
Now strain the thick tamarind water which was soaked two hours back. Add this to the kadhi and simmer for another 10 minutes.
For tempering, heat the oil in a tempering or small frying pan.
To the hot oil add mustard seeds, curry leaves, cumin seeds and red chilli powder and add this tempering to the kadhi.
Garnish with coriander leaves and serve hot kadhi with peas pulao or steamed rice.