Step 1

Turn the slow cooker to the High setting to heat up. Put the roughly chopped onions and curry paste in a food processor with 100ml/3½fl oz water and whizz until smooth. Scrape into the slow cooker, then add the thinly sliced onion, lamb chunks, cumin seeds, cinnamon and bay leaves.

Step 2

Use kitchen scissors to snip the plum tomatoes into small pieces inside the tin, then tip into the slow cooker. Give everything a good stir, season with salt and pepper and cover with the lid. Cook for 4 hours on High or 8–9 hours on Low until the lamb is tender, but not dry. If using the pepper, add for the last hour of cooking.

Step 3

Stir in the yoghurt and leave for 10 minutes before serving. Taste and season again if needed and serve with rice or preferred serving options.