Add chicken, salt, pepper and lemon juice to a bowl and mix well. Set aside for 20-30 minutes and allow to marinate.
In a pan, heat a table spoon of oil and add onions, ginger and garlic. Fry till onions are soft and translucent.
Add it to a mixer grinder with cashew nuts. Grind to a smooth paste, use 2-3 tablespoons of water if required. Set aside.
Heat 2 tablespoons of oil in a pan and place the marinated chicken pieces side by side. Cook on high heat for 2-3 minutes on each side. Remove from the pan and set aside.
In the same pan, add the remaining 2 tablespoons of oil and add the whole spices and saute for 30 seconds to a minute.
Add the onion cashew paste and cook for 5-6 minutes on medium heat till you see oil separating from the sides.
Reduce the heat to low and add the whisked yogurt, garam masala and salt. Cook for 2-3 minutes, stirring continuously till oil separates.
Add green chillies and ¾ cup of water. Mix well, cover & simmer on low heat for 15 minutes till chicken pieces are tender and cooked through.
Add pepper and kasuri methi, mix and simmer on low heat for 2-3 minutes.