Cut all vegetables into similar sized batons or cubes. Keep aside.
Heat 1 cup water in a pan. Add veggies that take longer to cook like yam, drumsticks and carrots to it. Add salt. Cover and cook on low heat for 5-6 minutes.
Now add the other veggies. Add more water if needed and cook for 5-6 minutes or till they are almost done. If you don't have some of these veggies, you can use gourds and squashes available or even veggies like broccoli, cauliflower, carrot, beans etc.
Add some more water and cook again for about 6-7 minutes till they are cooked but retain their shape.
Grind together half coconut along with 3-4 green chillies and 1 tsp. cumin. Make a thick paste. If you don't have fresh coconut, you can use coconut milk in its place.
Add it to the boiling vegetables. Cook further for 5 minutes till the veggies are soft but not mushy.
Turn off the flame and add whisked plant-based yogurt along with 1 tsp. coconut oil. Mix well. Taste and adjust seasoning.
Traditionally there is no tempering added but I like to add it as I enjoy its flavour. Feel free to omit this step. For tempering heat 1 tsp. coconut oil in a pan. Add mustard seeds along with asafetida. Allow to sputter. Now add curry leaves and red chillies and turn off the flame.
Tip the tempering in the avial and mix well. Serve your avial with boiled rice.
Notes
1. Do not overcook the vegetables. 2. Cook the longer cooking vegetables first. 3. You can use any vegetables you have at home. Just cut them uniformly. 4. In case you don’t have coconut oil, you can use any other vegetable oil. 5. If using raw plantain, immerse in water after cutting to prevent it from turning dark. 6. In case you are using yam, cook it well to avoid the pins and needles taste in the mouth. 7. You can increase or decrease green chillies depending upon how much heat you want.8. Traditionally no tempering is added to the avial. Only coconut oil with curry leaves is added to the cooked veggies. Please note that I like the tempering and hence have used it. It is completely optional and my touch to this wonderful dish.