In a large pot, bring 1 cup of water to boil with salt and turmeric. Add all the vegetables. Once it comes to a simmer, reduce the flame, partially cover the pan and cook until all the vegetables are cooked, but don’t let them get mushy.
In the mixer, grind the coconut, cumin, chillies to a very fine paste using as little water as possible.
Add this mix to the cooked vegetables in the pot. Add the rice-flour slurry to this and bring to a simmer until thickened.
Heat the coconut oil in a small tadka ladle and crackle the curry leaves in it. Pour over the avial. Serve hot with steamed rice, arachuvitta sambar and preferably, fried appalams / pappadams too!
Other vegetables you can add: Snake gourd, drumstick, peas.