Rub chicken with ground ginger, garlic and turmeric. place in large bowl with other marinade spices, yogurt and tomato. In a heavy skillet, fry onions in a few tablespoons of the oil until golden. put half the sauted onions in with the chicken marinade. marinate for 1 hour. boil rice with rice spices and 4-5 cups of water. reduce heat, cover and simmer until rice is half done. Drain and set aside. after chicken is marinated combine with cooking spices and 2 -3 inches of water and simmer until tender. chunk potatoes and fry with reserved oil from onions on high. potatoes should be crisp not greasy. when everything is ready, put oil from skillet and fresh oil in the bottom of a large heavy pot, with a tight fitting lid. scatter a handful of rice and all the lentils on the pot bottom. scatter chicken and marinade across the lentils. cover with potatoes and more rice. place egg slices and then the last of the rice. pour the rest of the oil and 1/2 of cold water in the mixture. cover pot and cook on high heat for 5 minutes. reduce heat. let simmer 1 hour. when serving make sure to dig through the layers. Biryani should be accompanied by lots of yogurt and lots of chutney.