Firstle, heat the ghee (clarified butter) in a large pan over medium heat. Add the black peppercorns, black and green cardamom pods, cloves, cinnamon, and mace, and fry for 1 to 2 minutes, or until the spices are sizzling and fragrant.
Now stir in the chopped onion, and fry for 8 to 10 minutes, stirring regularly, or until golden brown.
Add the garlic cloves and ginger. Stir in the ground coriander, cumin, red chili powder, fennel seeds, garam masala, yogurt, and salt, to taste.
Cover the pan with a lid, and then reduce the heat to low, and simmer for 10 to 12 minutes. Now let it cool.
Finally, Add 2 to 3 tablespoons of water to the sauce stir well and blend the gravy in a food processor.