Pre heat the oven to 325º F
In a large bowl place the lamb, and season it with salt and garam masala. Set aside, covered, for 30 minutes.
In a wide heavy ovenproof pot with a tight-fitting lid, heat the oil or clarified butter over medium-high heat. Add the cinnamon, cumin seeds, cloves, cardamom, bay leaves and black peppercorns and stir until fragrant. Add the garlic and ginger and stir-fry for 2 to 3 minutes, until aromatic. Add the onions and cook, stirring frequently, until very soft, 8 to 10 minutes.
Lower the heat and add coriander, cumin, mace, nutmeg, cayenne, and stir-fry for an additional minute.
Add the lamb and sear until browned. Add the tomato, turmeric, and salt and stir. Add the water and bring to a boil.
Add the rice and bring back to a vigorous boil, about 5 minutes. Cover tightly (wrap the pot lid with foil if necessary to make a better seal) and place in a preheated oven for 45 minutes.
Remove from the oven and let it stand for 15 minutes, still covered. This will help to absorb all the flavors into the lamb.
Serve hot, garnished with the toasted almonds.