I used 7 veggies to prepare this Kuzhambu. You can use little in each veggie, as it yields a lot after cooking. Also, chop all the veggies in the same size, for even cooking. Soak tamarind in hot water for 20 minutes, extract tamarind water and discard the pulp. Then pressure cook toor dal with 1/2 cup of water for 3 to 4 whistles and mash it slightly.
Measure and keep all the other ingredients ready. To the boiling water, add pumpkin, potato, raw banana, avarai and brinjal. These veggies get cooked easily. Once it is 3/4th cooked, switch off the flame and drain the water (I used the same water when boiling the kuzhambu). I cooked arbi, sweet potato and mochai separately in the pressure cooker.
Pour 1 tbsp of oil in a pan, add shallots, garlic and saute till it turns translucent. Then add tomatoes and saute until mushy. Now pour the tamarind water and let it boil for 2 to 3 minutes.
Add all the 7 veggies and pour 1 cup of water.
Now add turmeric powder, chilli powder, sambar powder, coriander powder and required salt.
Mix everything well and boil for 2 minutes in low flame.
Add the cooked toor dal and give a boil for another 2 minutes. Switch off the flame and add jaggery.
To a small pan, pour 1 tbsp of oil, add all the items listed in the table 'To Temper'. Pour it over the curry and mix well. Give at least 1 hour resting time for the kuzhambu, so the flavours get infused well.