Heat small frying pan on medium heat and toast fennel seeds for about 20secs or until give off sweet, aniseedy scent. Using pestle and mortar, pound them to powder and set aside.
Heat oil over medium heat in large, lidded ovenproof casserole and add cumin, cardamom, chilli flakes and cinnamon. Stir and fry spices until give off nutty aroma (about 20secs).
Add onions and fry for 10mins, stirring often, until golden. Add garlic, ginger and 75ml water; cook for 1min until water has evaporated.
Preheat oven to 170C. Tip lamb and bay leaves into pan and fry for about 10mins until well browned, stirring all the time. Add dash of water if meat starts to catch.
Stir in tomatoes, turmeric, green chillis, garam masala, potatoes, turnips and crushed fennel. Simmer for 5-7mins till tomatoes have cooked down.
Pour over stock, bring to simmer and cover. Transfer to oven for 1hr15mins, until meat is tender. Scatter with chopped coriander and serve with flatbreads or rice and some yoghurt.