Mix all the spice mix ingredients listed above along with ⅔ cup of peanut oil or more if preferred, in a big bowl and keep it aside.
If using frozen papdi and lilva, run them through extra warm water 2-3 times and let it sock in hot water for 5 minutes. Drain all the water out once done. This will help to get rid of the weird smell you get sometimes from frozen papdi and lilva.
Wash all the vegetables and get rid of as much water as possible.
Peel all the potatoes (except baby potatoes) and yams (except Frozen Indian Violate/Purple Yam). Cut them into medium sized chunks. Keep it aside.
Wash eggplants and remove stems. Make couple of cuts into each eggplant so the eggplant can hold the stuffing. Stuff each eggplant with the prepared spice mix. Keep them aside. Do the same for bananas, if you preferred them cooked and soft, if not follow last few step, referring to banana.
Add all the other prepared vegetables into leftover prepared spice mix. Mix it very well making sure all the vegetables are coated with the spice mix. It is best to let it marinade for couple of hours or more, but you can certainly skip the waiting part.
Add 4-5 tbsp of oil to a pressure cooker, either Indian style or an Instant Pot. Add carom seeds (ajwain), once they start to fragrant and turn brown, add asafetida (hing). Add half of the vegetables mix (not eggplant and banana). Mix it well with oil.
Place all the stuffed eggplant on top of it.
Add rest of the coated vegetables with all the spice mix into the pot, on top of the eggplants.
Rinse the big bowl that you had vegetables and spice mix in with ¾ cup of water. Add that water to the pot. Yes, it sounds odd but I would hate to waste any of the incredible spice mix, and I think it adds some extra flavor to Undhiyu. Trust me with it!
If you prefer banana cooked and soft, place them on top of last layer of the vegetable mix, along with methi muthiya. If you prefer not so soft banana, skip the banana step.
Close the lid and secure the valve.
When ready, Cook it on high pressure for 6 minutes. Let the pressure release naturally for 10 minutes once the cook time is over. After 10 minutes, release rest of the pressure manually.
If using Indian style pressure cooker, do 3 whistles and let the pressure release naturally.