The yams in this dish are cooked in a sauce very much like that traditionally used for meat. Serve with chapatis and rice. The recipe is derived from one in The Hamlyn Curry Cookbook, by Meera Taneja, which I recommend highly.
Peel the yams, cut them into 1 inch cubes, place in a colander and sprinkle liberally with salt. Let stand 10-15 minutes, then dry on paper towels.
Meanwhile, finely chop the onion, ginger, and garlic, and roughly chop the tomatoes. Heat the il over a moderate flame, add the cumin seed, and cook until they begin to splutter. Add the chopped onion, ginger, and garlic. Cook until the onion is a rich golden color. Add all the spices and season with salt to taste. Cook a few seconds more, and then add the tomatoes. Let this cook while you continue as below.
Heat the oil for deep frying to 350 deg. F and cook the yam cubes, a few at a time, until golden brown. Drain on absorbent kitchen paper. Set aside.
Add the yogurt to the tomato mixture, and continue to cook until the oil begins to separate out. Add the water and bring to a boil. Let boil a few minutes, then add the yam cubes, reduce heat, and simmer, covered, for about 25 minutes.
Serve hot, garnished with the chopped coriander.
Difficulty: easy to moderate. Time: 1 hour preparation, 30 minutes cooking. Precision: measure the ingredients.