Soup: Heat the oil in a large pot and brown the shanks.
Remove from the pot and add the onions, garlic, ginger, saffron, cumin, cardamom, chilli and cinnamon.
Fry gently without burning until the flavours have developed. Add more olive oil if necessary.
Return the meat to the pot and add the tomatoes, stock and lentils. Simmer gently until the meat is tender.
Season with salt and pepper to taste.
Minted yoghurt: Mix the yoghurt, mint and chilli.
Ladle the soup into bowls or mugs and garnish with the minted yoghurt.