1.3kgBoneless lamb shoulder, cut into chunks of about 4cm
100mlRed wine vinegar
2tbspVegetable oil
2Bay leaves
500gramsPotatoes, peeled and cut into 2.5cm chunks
Flaked sea salt
For the sauce
125mlVegetable oil
4Onions, 3 thinly sliced and 1 chopped
6cloves ofGarlic cloves, roughly chopped
3Long red chillies, (do not deseed), roughly chopped
25grams ofFresh root ginger, peeled and roughly chopped
1tbspEnglish mustard powder
1tbspGround cumin
1tbspGround coriander
1tbspGround paprika
2tspGround turmeric
2tspCayenne pepper
1tspGround cinnamon
Instructions
Trim the lamb, discarding any really hard lumps of fat and sinew
Mix the vinegar and vegetable oil with 2 teaspoons of sea salt in a non-metallic bowl until well combined, then add the lamb and turn it to coat in the marinade
Cover and leave in the fridge for 2 hours to marinate
For the sauce, heat 3 tablespoons of the oil in a large heavy-based frying pan
Cook the sliced onions very gently over a medium-low heat for 15 minutes until they’re softened and lightly browned, stirring occasionally
While the onions are cooking, put the remaining chopped onion with the garlic, chillies, ginger, mustard powder, cumin, coriander, paprika, turmeric, cayenne pepper and cinnamon in a food processor and blend to a purée
Stir this purée into the fried onions
Add 2 tablespoons of oil and cook together for 5 minutes, or until the sauce has thickened and is beginning to colour
Tip the mixture into a flameproof casserole dish
Drain the lamb in a colander over a bowl, reserving the marinade
Return the frying pan to the heat and add 2 tablespoons of the remaining oil
Fry the lamb over a medium high heat, turning occasionally until lightly browned – do this in 4 or 5 batches, adding a little extra oil if necessary
Add each batch of lamb to the casserole as it is browned
Preheat the oven to 180°C/160°C Fan/Gas 4
Pour the reserved marinade and 500ml water into the casserole dish, then add 2 teaspoons of salt and the bay leaves and bring to a simmer
Cover the surface of the curry with a piece of greaseproof paper, then put a lid on the dish. Cook in the oven for 45 minutes
Remove the casserole from the oven and stir the potato chunks into the curry
Replace the greaseproof paper and the lid and continue to cook for a further hour or until the lamb and potatoes are very tender
Check the seasoning and add salt to taste
Serve with some rice or warmed naan bread and a bowl of cooling yoghurt on the side.