Add all the cut vegetables except mangoes to a large cooking pot (we usle the traditional kal chatti or stone pot to make aviyal at home). Top off with half the turmeric powder, jeera, curry leaves, and chilli powder. Add about 1/2 to 3/4 cup water and mix well.
Cook covered on a low flame for about 10-12 mins or until the vegetables are cooked yet hold their shape.
Meanwhile, grind together - coconut+green chillies+ remaining turmeric+some more curry leaves to a coarse paste without adding water.
Check that, is your vegetables are almost cooked through
Add the ground coconut mixture on top along with required amount of salt and the mango strips. Without mixing, cook covered for another 3-4 mins.
That's it! Mix the coconut mixture in gently and remove from flame. The avial will be a bit watery still but it will dry up as the vegetables absord it as they sit.
Sprinkle the coconut oil on top and mix gently. Set aside covered loosely for an hour before serving.