Heat ¾ cup oil in a small frying pan and fry the potatoes until golden, about 10 minutes.

In a large saucepan, heat ½ cup oil and fry the onions until golden. Remove with a slotted spoon and drain on paper towels. Set aside. Add the whole spices to the same oil and fry for 1 minute, then add powdered spices, salt and pepper, passata and garlic, and cook over a low heat for 6-8 minutes. Add the lamb pieces and cook, covered, for a further 10 minutes. Add tomato paste, vinegar and fried potatoes and simmer until the sauce clings to the meat, about 10 minutes. If it starts catching on the bottom, add a splash of water. The sauce should be a thick consistency and not too runny. Turn off the heat.

Soak the rice in water for 20-30 minutes. Drain then wash the rice until the water runs clear. In a large saucepan, heat the oil and butter, add the rice and stir until it just starts to become translucent, then add just-boiled water and salt. Allow to boil for 1-2 minutes, then turn the heat down to low and simmer, covered, for about 15 minutes until the water has evaporated. The rice should be cooked, fluffy and separated.

Mix 1 cup of the cooked rice with a drop of red and yellow food colouring mixed with a little water. Soak the saffron in 1 Tbsp just-boiled water for a few minutes then stir into the coloured rice and set aside.

Place a layer of curry into a large 2-litre capacity ovenproof pan. Add a layer of cooked white rice to the pan, then a layer of the curry, and carry on until you have 3-4 layers, ending with rice.

Place the boiled eggs on top and then add your saffron rice, fried onions and chopped coriander.

Preheat the oven to 180°C bake.

Unroll the filo pastry and cover with a damp cloth. On a clean work surface, one at a time, place a pastry sheet with the long side towards you and brush with butter. Fold roughly concertina style lengthways and then roll up to form a rosette. Repeat with remaining filo. Place each rosette on top of the biryani until it is fully covered.

Drizzle with a little oil or ghee around the edges so it drips down the sides of the biryani.

Bake for 20–25 minutes or until the filo roses are golden.

Decorate with Persian tea rose petals, if desired. Serve hot with a cucumber raita and tomato and onion kachumber.