Soak cashews in half a cup of hot water for 30 minutes and grind them to a fine paste. Mix yogurt and set this paste aside.
Heat butter/oil in a handi. Add the whole spices - cinnamon, green cardamom, and cloves. Lightly fry till it emanates a good aroma. Add finely chopped onions and fry till golden brown in color. Add the ginger-garlic paste. Once cooked, add the chopped coriander and mint leaves. Stir and saute for a minute.
Add the chicken pieces and saute till light brown on all sides. Add turmeric powder, red chili powder, salt, and coriander powder. Give it a stir. Mix in the finely chopped tomatoes and cook till the tomatoes soften and you see oil leaving the sides of the pan.
Add the ground cashew paste and yogurt. Keep stirring till oil starts leaving the sides of the masala. Add the slit green chilies and garam masala powder, stir again and let the gravy simmer for 3 to 4 minutes on a low to medium flame.
Garnish with chopped coriander or mint leaves.
Serve Chicken Handi with tandoori rotis, naan, parathas or chapatis.