Heat up a large heavy-based saucepan over medium high, add a splash of oil, the onion and the fennel. Cook 5 minutes, stirring, until soft.
Add the chilli, garlic, paprika and saffron and cook 2 more minutes, stirring all the time. Add the tomatoes and cook briefly to soften them up, then add the bay leaves and stock and bring to the boil. Add the potatoes and salt to taste and cook 15 minutes or until the potatoes are done.
Add the fish and let just cook through. Check for seasoning and serve, garnished with coriander.