Heat your oven to 180°C/Fan 160°C/Gas 4. Tip the rice into a small pan and cover with 300ml boiling water. Pop on a lid and return to the boil, then reduce to a simmer and cook for 5 mins. Drain well and set aside.
While the rice cooks, peel 1 of the onions and finely chop it. Peel and crush or finely grate the garlic. Peel and grate the ginger. Halve the chilli, scraping out the white membrane and seeds for less heat, and finely chop the chilli. Finely chop the tomatoes.
Pour 1 tbsp oil into a medium ovenproof pan (pan not ovenproof? See our tip at the end) and warm over a high heat. Add the lamb and fry for 5 mins, turning once or twice, till browned. Scoop out of the pan into a bowl and set aside.
Reduce the heat under the pan to medium and add a little more oil if needed. Slide in the chopped onion and sprinkle in a pinch of salt and pepper. Fry for 3 mins, stirring occasionally, till softened. Stir in 1 tbsp of the tikka spice, 1 tsp turmeric and the garlic, ginger and chilli. Continue to cook for 1 min, till fragrant.
Slide the lamb back into the pan and add the chopped tomatoes and the spinach. Stir till the spinach is wilted then remove from the heat.
Add the drained rice to the pan and stir well. Flatten the surface of the rice with a spoon and pour over 150ml boiling water. Pop a lid on the pan and slide into the oven. Bake for 20 mins. After 20 mins, remove the lid from the pan and return to the oven. Cook for another 5 mins.
While the biriyani cooks, peel and thinly slice the remaining onion. Pop the slices in a bowl and toss with 1 tbsp tikka spice mix. Pour 1 tbsp oil into a pan and bring to a high heat. Slide in the onions and fry for 5-6 mins, stirring frequently, till golden and crisp at the edges. Slide onto a plate lined with kitchen paper to drain.
Roughly chop the coriander leaves. Cut the pomegranate in half. Hold 1 half in your hand, cut-side down, and whack it with a wooden spoon. The seeds should fall through your fingers. Catch them in a bowl and repeat with the other half.
Spoon the biriyani onto warm plates and top with the spiced onions, pink pomegranate seeds and coriander leaves to serve.