Place the lamb in a large bowl and add the onion mixture and the egg. Mix well by hand or with a large spoon.

Transfer the mixture to an airtight container and leave in the fridge for a few hours, or overnight, to marinate. This helps the flavours to infuse.

When ready to cook the curry, shape the meatballs into 20 walnut sized balls. I divided the mixture into half, then half again to make the balls as evenly sized as I could. Wetting your fingers and palms helps with the rolling.

To prepare the curry, heat the vegetable oil in a heavy based saucepan.

When the oil is hot, add the whole spices. When the cumin seeds begin to sizzle add the onion, garlic and ginger mix.

Fry this mixture until it is golden to dark brown. This might take awhile, but be patient - it's an important step in making the curry taste amazing.

Add the chopped tomatoes, tomato purée, ground coriander, turmeric, chilli powder, paprika and salt. Cook until the oil separates or the mix looks shiny.

Add the water, bring to a boil and reduce the heat to a simmer.

Add the meatballs, raw, to the simmering (but not boiling!) sauce. Allow to simmer for 20 minutes, with the lid off (covering with the lid sometimes causes the meatballs to break), shaking the pan on occasion and turning once.

When meat balls are ready, any oil will separate and float to the top of the sauce. Add half the coriander leaves and garam masala, stir gently and transfer to a serving dish.

Garnish with remaining coriander and serve hot with freshly made chapattis, steamed rice or plain pilaf rice.