The sauce is a base of Onion-Tomato-Ginger-Garlic and is flavored with Garam Masala spices such as Cinnamon, Black Cardamoms, Cloves, Star Anise and Bay Leaves. Most of these spices are big enough so that they can be easily fished out after the dish is cooked. The only exception is Cloves, which are harder to spot after the dish is cooked, so I crush the Cloves as part of the sauce base. Note that, while this recipe calls for adding whole Garam Masala spices, you can choose to instead add Garam Masala powder at the end.