Heat oil in large pan with lid over medium high heat
Add peppercorns, cloves, bay leaves and cardamom pods- stir for a minute
Add onion, garlic and ginger. Fry until onions are golden brown
Add cumin, coriander, cayenne, mustard seeds, chili, turmeric and 1 tsp salt. Stir for 60 seconds
Add lamb and seal for 60 seconds
Add tomato paste and stir until well mixed
Add yoghurt one tablespoon per minute until all yoghurt incorporated and meat is browned
Add spinach and remaining salt, stir until wilted
Cover with lid and simmer on low for 80 minutes or until lamb is tender
Add garam masala and stir until desired thickness of sauce is reached
Ideally remove at least cardamom pods and bay leaves, remove cloves too if you can find them!