Bengali Lamb Kosha

Name: Bengali Lamb Kosha
Ingredients: 1 Kilo Lamb leg of lamb, diced; 1 piece lamb bone; 40 grams butter; 500 grams onions blended to a paste; 200 grams tomatoes blended to a paste; 4 tablespoons yoghurt; 1 tablespoon ginger and garlic paste; 1 piece cinnamon stick; 2 bay leaves; 3 green cardamom; 5 cloves; 1 teaspoon black cumin seeds or normal cumin seeds; 1 teaspoon ground cumin; 1 tablespoon ground coriander; 1 teaspoon tumeric; 1,5 teaspoons salt; 2 tablespoons oil; 1 teaspoon kasoori methi; 3 potatoes peeled and halved; 2 green chilies chopped; 1 teaspoon sugar; fresh coriander; 1 teaspoon garam masala