To make the meat curry, first heat 4 tablespoons of oil in a large, heavy frying pan. When the oil is very hot, add the meat and bones and brown. If the amount of meat is too large, roast the pieces in several stages. Remove the finished roasted meat from the frying pan with a slotted spoon.
Add the remaining 4 tablespoons of oil to the frying pan, then the onions. Reduce the temperature to medium and roast the onions until dark brown, stirring throughout (about 20 minutes).
Add the ginger and garlic and fry for a minute. Add cumin, coriander, turmeric and cayenne pepper and fry until spices release their aroma (about 10-15 seconds). Add curry paste.
Return browned meat and bones to pan. Add tomatoes, salt and 1 liter of boiling water as well. Bring to a boil. Then turn heat down to low, cover and simmer for 1 1/2 hours.
Add the potatoes and simmer until they are soft and the meat is tender (about 30 minutes). Then turn off the heat and let the dish sit for at least 30 minutes, but preferably 2 hours.
Remove the bones before serving or leave them in, season the meat curry with salt and heat thoroughly. Stir in the coriander leaves and serve.