Heat butter, Pan-fry marinated chicken till lightly brown, dish up for later use.
Sauté chopped onion, garlic, ginger and green chillies in butter, fry till aromatic, toss in garam masala. Add in tomato cook till soft and add in seasoning.
Pour the tomato mixture into a blender; puree the mixture and bring back to boil. Add in cashew nut paste stir till gravy slightly thicken, add in the chicken and cook for 5 minutes till chicken tender.
Transfer into a serving plate and serve with steamed rice.