Heat the fat in a heavy pan and cook the onion and garlic for 3-4 minutes. Add all the other ingredients, except the meat and the tamarind, and cook over a low heat for 5 minutes or so. Add the meat and stir thoroughly. Cover the pan and cook for 5-10 minutes.
Add a teacupful of water, cover the pan closely again, and simmer until the meat is cooked. This will take anything from 40-60 m