Place the lamb, ginger, garlic and olive oil in a medium-sized bowl with a generous pinch of salt. Mix together and cover with cling film. Place in the fridge overnight.
Preheat the oven to 180°C, gas mark 4.
Fry the onion in butter for 7-9 minutes, until caramelised.
Add the marinated lamb and fry for 5 minutes, until browned all over.
Add the rice, nutmeg, turmeric, curry powder, cardamom pods, cinnamon stick, green chillies, cumin seeds and bay leaves to the pan and fry for 2 minutes.
Transfer everything to a casserole dish.
Add the frozen peas, raisins and chicken stock to the dish and cover loosely with aluminium foil.
Bake in the oven for 25-35 minutes, until all the liquid has evaporated, the rice is tender and the grains are starting to separate from one another.
Garnish with the mint leaves and toasted almond flakes.