Heat oil over medium heat in wok. Add the onions and ginger. Cook 5 to 7 minutes on low/medium heat, stirring frequently. Do not brown. Add spices and cook 2 minutes more. Add tomatoes, heavy cream, salt, sugar, pepper and 1/2 cup water. Bring to a boil, then reduce the heat to medium-low and simmer, uncovered, until thickened, about 15 minutes.
Add chicken tikka, fish or prawn to the sauce and simmer until cooked.