We need a jihad/crusade on this aunties pantry, I will personally take all the egg plants and set them on fire.
Seriously, eggplant in biryani, that's heresy. Eww I can't even imagine the taste.
Coming to potatoes, I think it has something to do with poverty and people's standards of living. The potatoes are used as replacement for meat, they're tasty, filling and cheap.
Potatoes have for long been the one true champion for poor and impoverished people in their neverending fight against starvation.
If you notice we Bengalis don't eat as much meat as compared to pakistanis or Indians (non veg Indians), I think this is because our people still have an atavistic trait from our 'khete khawa' days of poverty.
Overtime, this has changed as we eat more meat now than ever but we still a long ways off. We also need a lot more milk in our diet.
Apologies for going wayward, I get carried away easily.
Coming back to the topic at hand, I enjoy potatoes in Biryani and I wouldn't have it any other way. I don't think there's any bangali out there who is against potatoes in their Biryanis.
Potatoes have a earned a place in our heart, our bellies and in our Biryanis.