From an Old Indian Aunty this is so tasty

OK this is the real deal that is as good as any lamb or mutton curry you will find in the finest Indian restaurants (or in some of Durbans fine home kitchens). It takes a while to make but is not complicated. Feeds (6 people)

What you need

1/2 cup plain yogurt
1 teaspoon cumin
2 teaspoons white vinegar
2 tablespoons grated fresh ginger
3 teaspoons chili powder
1 teaspoon turmeric
1kg mutton chunks (approx 3cm cubes) You can use lamb as well but this curry is tradionally made with mutton.
Oil
2 large potatoes in chunks similar in size to the mutton
1/2 teaspoon cinnamon
pinch of cardamom
2 teaspoons crushed garlic
1 teaspoon sugar
3 medium onions halved and sliced
2 bay leaves
2 tablespoons tomato paste
1 cup water

The process

In a bowl combine mix together yogurt, cumin, vinegar, ginger, chili powder, and turmeric, mix well and then add your meat, cover and marinade in the fridge for 3 to 4 hours for mutton and 2 hours for lamb.

Add about 1cm of oil to a heavy base pot or stainless steel casserole dish on a medium to high heat and cook the potatoes until browned. Remove and drain on paper towel.

Remove some of the oil, reduce the heat to medium low and add the onions, cinnamon, cardamom, garlic and sugar and cook to soften the onions. Add the potatoes now and the meat to the pan and cook for about 5 minutes stirring occasionally.

Add the water, bay leaves and tomato paste, bring to a boil, reduce the heat to low, cover and simmer for 1 hour, check that there is enough water and add about another 100ml if necessary, stir and simmer for another 1/2 hour.

Now check that the sauce is thick and quite sticky and if not, simmer for another few minutes with the lid off.

Eat with a good Basmati rice or make a Bunny chow however you eat this it's all good