Pick, wash and soak rice in sufficient water for about twenty minutes. Drain. Peel, wash and chop one onion finely and slice the others. Peel and wash ginger and garlic. Remove stems and wash green chillies. Grind ginger, garlic and green chillies to fine paste. Wash and chop tomatoes finely. Add ginger, garlic and green chillies paste. Add coriander powder, turmeric powder, red chilli powder, yogurt and mix well.
Peel, wash and cut carrot into half inch sized pieces. Separate cauliflower into small florets, wash and drain. String, wash and cut French beans into half inch sized pieces. Wash and drain green peas. Clean, wash and chop coriander leaves and mint leaves separately. Soak saffron in kewra water.
Boil drained rice in four cups of salted boiling water with green cardamoms, black cardamom, cloves, cinnamon and bay leaf, until three-fourth done. Drain excess water and keep aside. Mix all the vegetables and boil in three cups of salted water till three-fourth done. Drain and refresh under running water. Keep aside.
Heat sufficient oil in a kadai and deep-fry the sliced onions till golden brown. Drain onto an absorbent paper and keep aside. Heat two tablespoons of oil in a thick-bottomed pan. Add caraway seeds and cumin seeds. When they begin to change colour, add chopped onions and sauté until golden brown.
Add chopped tomatoes and cook on a medium heat till fat leaves the masala. Add boiled vegetables and salt mix well. Preheat oven to 275°C. Take a handi, arrange alternate layers of cooked vegetables and rice. Sprinkle saffron dissolved in kewra water, garam masala powder, coriander leaves, mint leaves, golden fried sliced onions and butter in between the layers and on top.
Make sure that you end with the rice layer topped with saffron and spices. Cover and seal with aluminum foil or roti dough. Cook in the preheated oven, for ten minutes at 275°C. Reduce temperature to 225°C and cook for another ten minutes. Alternately keep the handi on a tawa and cook on low heat for fifteen minutes.
Serve hot with a raita of your choice.