Put the chicken (that has been marinating in the spices) into a large fry pan over medium heat until cooked through.
In a large sauce pan, put the oil, garlic, and ginger over medium heat until it starts to simmer. Then add the remaining spices (except salt and masala) and simmer for another minute. After that, add the tomatoes and simmer for 3 to 4 minutes. Add the yogurt and blend in with a wire whisk. Then add the cooked chicken pieces, the 3/4 cup water, and salt. Bring to a boil, then cover and simmer for 20 minutes.
Stir in the coconut milk and garam masala then simmer uncovered, stirring occasionally, until the sauce becomes fairly thick. Serve with rice.