1 kg lamb, cubed 1 medium onion, sliced thinly into rings 2 large tomatoes or 1x400g tin chopped tomatoes 2 Tbsp vegetable oil 2-3 curry leaves 1 stick cinnamon 4 green cardamom pods, lightly crushed 1.5 tsp crushed ginger 1.5 tsp crushed garlic 4 tsp Durban masala (or substitute shop-bought curry powder,as hot or mild as you like) 1 tsp ground turmeric 2 tsp garam masala 3-4 potatoes, cubed