If using the chicken, pat dry with kitchen paper, score the skin and sprinkle with sea salt. Heat the oil in a large flat pan. Place the chicken in skin side down and allow to crisp and brown. Turn over and brown the other side for about 2 minutes. Remove from the pan and set aside.
Turn the heat down to low-medium heat using the same pan and oil. Cook off the onions, ginger and garlic for about 5 minutes until soft and every aromatic.
Add in the korma paste and rice and cook for about 2 minutes.
Add in the potatoes and cauliflower. Add in the stock pot and cover with water. Stir well.
Sit the chicken on top.
Pop the lid on ( or cover with foil ) and cook in the oven for about 45 minutes.
After 30 minutes, remove from the oven. Lift the lid and toss through the spinach/peas. Cover again and pop back in for about 10 minutes. Taste and add salt or a pinch of sugar if needed. Add a squeeze of lemon juice.
While the biryani is cooking, toast the cashews in a dry pan until golden. Set aside.