I used these vegetables for avial: drumstick, cluster beans, broad beans, beans, snake gourd, carrot, potato and plantain.
Cut them into long strips kind of pieces.
I boiled the first 4 vegetables above first, along with curry leaves.
After that vegetables are half done, added rest of the other.
I added plantain lastly as it takes less time to get cooked.
You can pressure cook all the veggies together too for just two whistles with very little water.
While the veggies get cooked, grind coconut, green chillies and rice flour with cumin seeds, little water, to a coarse paste.
And add this coconut mixture to the cooked vegetables
Let it come to boil. Remove from fire.
Then add the well beaten curd.
Mix in the curd and temper the aviyal with coconut oil, mustard and curry leaves.
Finally add coconut oil raw as garnish.