This rich and aromatic curry would usually take hours of gentle simmering, but once you’ve marinated the lamb – for an hour, or overnight – you can cook it in 20 minutes in the pressure cooker.
Put the lamb in a bowl. Put the garlic, ginger, salt and pepper in a mini processor with 1 tablespoon of the oil and pulse to form a paste. Add to the lamb and stir to coat. Leave to marinate for at least 1 hour, or overnight in the fridge.
Heat the remaining 3 tablespoons oil in the pressure cooker over a medium–high heat. Add the lamb and fry for 5 minutes, or until beginning to brown.
Add the onion and fry for 4–5 minutes, or until softened. Add the chilli powder, ground coriander, turmeric, cumin, garam masala and fenugreek. Stir for 2–3 minutes, until the lamb is well coated in spices and is beginning to smell fragrant.
Add the potatoes, 400ml/14fl oz water and a whole green chilli and stir. Fix the lid on the pressure cooker and place over a high heat until it reaches pressure. Reduce the heat and cook for 20 minutes. (If using an electric pressure cooker, use the high pressure setting for 20 minutes.)
Remove the pressure cooker from the heat and leave to depressurise.
Remove the lid and stir the yoghurt through the curry. Taste and add more salt if necessary. Serve with basmati rice, garnished with sliced green chilli, ginger slivers and plenty of fresh coriander.