Heat the oil in a large pot over a medium-high flame. When hot, put in the peppercorns, cloves, bay leaves, and cardamom pods. Stir for a second. Now put in the onions, garlic and ginger. Stir and fry until the onions develop brown specks. Now add the meat, ground cumin, ground coriander, cayenne pepper, and 1q/2 of the salt. Stir and fry for a minute. Add 1 tablespoon of the yogurt. Stir and fry for a minute. Keep doing this until all yogurt has been incorporated. The meat should also have a slightly browned look. Add the spinach and the remaining salt. Stir to mix. Keep stirring and cooking until the spinach wilts completely. Cover tightly and simmer on low heat for about 1 hour or until meat is tender. Remove the lid and add the garam masala. Turn the heat to medium. Stir and cook another 5 minutes until most of the water in the spinach disappears and you have a thick, green sauce. Remove the whole spices and serve.