Sauté onion in oil in a 4 to 6 quart pan or Dutch oven till transparent. Add all ingredients in rapid succession and cook on reduced heat stirring continuously to prevent sticking on bottom and scalding. Add salt and 2 cups of water still stirring and increase heat so that water comes to a boil and makes a thick sauce. Add remaining water and stir into smooth consistency. Now reduce heat and add shrimp or chicken and potatoes. If using shrimp allow curry to cook for about l5 minutes and then add shrimp and cook for 10 minutes more. Serve over white rice with kachumber.