Add about 1 cup of water to a pan and bring water to boil. Add chopped onions and cook them. Strain the water and cool the onions. Once the onion comes to room temperature, blend them into a fine paste without adding water
Add water to the pan again and bring water to boil. Cook the cashew and cool. Blend them into a fine paste by adding little water
Add oil and butter to the pan, when the pan is hot, add cinnamon, fennel seed powder and cardamom, and sauté for ½ minute.
Add onion paste and ginger garlic paste and saute for 3-4 minutes
Add cashewnut paste and continue to sauté for 2-3 minutes
Add milk and 1/2 cup of water. When the mixture comes to boil, add heavy cream and green cardamom powder
Place the koftas in a serving dish and pour the gravy over the Kofta (Make sure the koftas are in room temperature, else they will break)