Boil sliced onions and cashews in water for 8 minutes; blend into a smooth white paste.
Heat ghee in a heavy pot, add ginger paste, garlic paste, and chicken breast pieces; sauté for 5 minutes.
Stir in whisked yogurt, white cashew-onion paste, whole green chilies, and salt.
Pour in water, cover, and simmer on low heat for 20 minutes until chicken is tender.
Finish with garam masala before serving.