In a large bowl, combine mustard oil, spices, ginger-garlic-green chilli paste, hung curd, lemon juice, and salt. Add paneer cubes and coat them well in the marinade. For a smoky flavor, place a live charcoal piece in a bowl in the center of the paneer, pour ghee over it, and cover for 3-4 minutes. Discard the charcoal safely afterward.

Wash basmati rice in a large bowl until the water runs clear. Soak the rice for 45 minutes to 1 hour.

Heat a nonstick pan over high flame. Add ghee, then the marinated paneer pieces, and cook until golden brown on both sides. Remove from the pan.

Add the marinated vegetables (onions, capsicum, tomatoes) to the same pan. Sauté quickly on high flame to retain their crunch, then set aside.

Heat oil in a heavy-bottomed vessel. Add sliced onions and sauté until golden brown. Add ginger-garlic-green chilli paste, turmeric powder, and degi red chilli powder. Sauté, then add grated tomato and cook for a few minutes. Lower the flame, whisk curd with leftover marinade and biryani masala, and add it to the gravy. Cook until the oil separates.

Spread the cooked paneer and vegetables evenly over the gravy. Sprinkle chopped coriander and mint.

Bring water with whole spices, green chilli, lemon juice, and lemon slices to a boil. Add the soaked rice and cook until 80-85% done, about 4-5 minutes. Drain half the rice and layer it over the paneer and vegetables. Add more coriander, mint, and crispy fried onions (birista). Repeat with the remaining rice and garnish with saffron water mixture and ghee.

Cover the handi with a muslin cloth and place a lid on top. Heat a tawa over medium heat, place the handi on it, and cook on high heat for 10 minutes. Reduce the flame and cook for another 10-15 minutes on low heat. Let it rest for 30 minutes before serving.