Preheat large sauté pan over medium-high heat. Using a mortar and pestle (or small food processor), make a paste of the garlic and ginger.
Add oil to pan, then chicken pieces. Cook until chicken is browned on all sides, then add onion and garlic-ginger paste. Stir frequently until the onion, garlic and ginger start to get some color, about 3-5 minutes. Add curry powder and sauté for a minute. Stir in salt, diced tomatoes and coconut milk. Lower heat to medium, cover and simmer about 5 minutes.
Cook the chicken until it is fork-tender and no longer pink inside. Raise heat to medium-high, 3-5 minutes, or until sauce starts to thicken. Add peas and cilantro, stirring to heat through, 2-3 minutes.
Serve immediately over rice, and enjoy! (And hope for some leftovers for lunch tomorrow...)