Add the onion and garlic to a frying pan with the butter/oil and sweat for 2 minutes. Add the ginger. Mix. Add the tin of tomatoes, peas and 150ml water. Add the curry powder, cardamom, cloves, cayenne pepper, salt, cumin turmeric and sugar. Combine well. Simmer for 5 minutes.
Add cooked lamb. Turn the heat down slightly. In a bowl mix the yoghurt with the flour well. Stir into the curry mixture. If the curry is too thick you can always add some more water. Leave to simmer on low heat for 10 minutes. Turn up the heat a couple of minutes before serving.