To make the Omani spice paste:.
Combine all ingredients in an electric food processor and process until a thick paste is formed, adding more vinegar if necessary. Keep aside.
Put lamb pieces and water in a large pot, bring to boil and remove froth as it appears. Add the cinnamon sticks, and all whole spices. Cover and simmer over low heat for 1½ hours or until the meat becomes tender. Remove lamb pieces, put them in a bowl and set aside. Drain the stock and set aside.
Cook the extra water and onion in a large sauce pan with occasional stirring for 5 minutes or until water is steamed and the onions become tender.
Add 2 tablespoons of the ghee (reserve 2 tablespoons) and stir for another 3 minutes or until onions become golden in color. Add garlic, raisins, chickpeas, 1 tablespoon of Omani mixed spices (reserve 3 tablespoons), saffron strands and rose water, stir for 1 minutes then set aside.
In a large pot put 4½ cups of drained stock; add more water if stock is not enough. Add the remaining 2 tablespoons of ghee, the remaining 3 tablespoons of Omani mixed spices, the Bouillon cubes and rice.
Bring to boil with occasional stirring, cover and cook over low heat for 10 minutes or until rice is half cooked, add the boiled lamb pieces on top of the rice, cover and cook on low heat again for another 10-15 minutes or until rice is cooked.
Serve the rice and lamb in plate topped with the onion mixture.