Put the chicken in a bowl with the turmeric, cumin, coriander, chilli and yogurt and mix well. (If you have more time, allow the chicken to marinate for longer. Just cover the bowl with clingfilm, then place in the refrigerator.)
Heat the oil in a heavy-based saucepan. Add the onion, garlic, ginger, cinnamon, cloves and cardamom and fry for 3–4 minutes.
Add the chicken mixture and cook for 2–3 minutes, stirring often. Stir in the rice and pour in the stock. Season generously with salt and pepper and bring to the boil. Add the potatoes, cover the pan tightly and reduce the heat. Simmer gently for 10–12 minutes.
Remove the pan from the heat and leave it to stand, without removing the lid, for 5 minutes. Fluff up the rice with a fork, garnish with sprigs of coriander and serve the biryani with poppadums and Indian chutneys.