Marinate the Beef: In a large bowl, combine the beef cubes with yoghurt, ginger-garlic paste, red chilli powder, turmeric, garam masala, ground cumin, ground coriander, lemon juice, and salt. Mix thoroughly until every piece is coated. Cover and let it marinate in the refrigerator for at least 1 hour, or ideally up to 4 hours.

Fry the Onions (Birista): While the beef marinates, heat the vegetable oil in a large, heavy-bottomed pot or Dutch oven over medium-high heat. Add the thinly sliced onions and fry, stirring occasionally, for 15-20 minutes until they are deep golden brown and crispy. Use a slotted spoon to remove the onions to a plate lined with kitchen paper. Spread them out to cool. Reserve about 4 tablespoons of the flavourful oil.

Cook the Beef Curry: In the same pot, add 4 tbsp of ghee (or the reserved onion oil). Once hot, add the marinated beef. Sear the meat for 5-7 minutes until it's browned on all sides. Add the chopped tomatoes and half of the fried onions, crushing them slightly with your hand. Stir well and cook for 10 minutes until the tomatoes soften and the oil begins to separate.

Slow-Cook to Tenderness: Add about 250ml of hot water to the pot, bring to a simmer, then reduce the heat to low. Cover the pot and let the beef cook for at least 1 hour and 15 minutes, or until it is completely tender and falling apart. Stir occasionally to prevent it from sticking. The resulting curry should be thick, not watery. Stir in the chopped mint and coriander.

Par-Cook the Rice: About 30 minutes before the beef is done, rinse the basmati rice in cold water until the water runs clear. Soak it in fresh water for 20 minutes. Bring a large pot of water to a rolling boil. Add the salt, cardamom pods, cloves, bay leaf, and cinnamon stick. Drain the soaked rice and add it to the boiling water. Cook for 5-6 minutes only, until the rice is about 70% cooked (it should still have a slight bite). Immediately drain it in a colander.

Layer the Biryani: Take a heavy-bottomed pot with a tight-fitting lid (the Dutch oven works well). Spread half of the par-cooked rice in an even layer at the bottom. Spoon the entire beef curry over the rice. Top with the remaining rice. What works best for me is using a pot that allows for generous layers without being too full.

Add Final Flavours: Soak the saffron threads in the warm milk for a few minutes. Drizzle the saffron milk and the melted ghee over the top layer of rice. Sprinkle over the remaining crispy fried onions, and some more fresh mint and coriander.

'Dum' Cook to Perfection: Cover the pot with a layer of foil and then place the lid on tightly to create a good seal. Place the pot on the lowest possible heat on your hob. Let it cook on 'dum' (steam) for 20-25 minutes. After this time, turn off the heat and let it rest, still sealed, for another 10 minutes. This step is crucial for the flavours to meld.

Serve: Open the pot and gently fluff the rice from the sides with a fork or wide spoon, trying not to break the grains. Serve the Beef Biryani hot, ensuring you get a mix of the rice and the beef masala in each portion.