1. To make the mussel and saffron stock, put the mussels and 250ml (1 cup) water into a saucepan. Place the pan over high heat with a lid on until the mussels begin to open, then remove from the heat. Strain the liquid to remove any grit from the mussels and reserve this juice. Remove the meat from the shells when cool and discard the shells. (Discard any mussels that do not open.)

2. Heat the olive oil in a large, heavy-based saucepan and add the onion, leek, fennel and garlic with a little sea salt. Cook over a medium heat until soft but not caramelised. Add the reserved mussel juice, chicken stock, tomato and saffron (and its soaking water) and bring to a simmer, skimming off any impurities, for 15 minutes. Remove the pan from the heat and pass the stock through a food mill or coarse sieve, forcing as much through as possible.

3. To make the risotto, melt half the butter and with the oil in a large saucepan. Add the onion and garlic and cook slowly until translucent. Add the rice and stir to coat all the grains in the butter, then cook for 30 seconds. Pour in the wine and allow it to reduce completely, then add the mussel and saffron stock (you'll use about 4 cups), ladle by ladle, stirring all the time and allowing each ladle to be absorbed before you add the next. Continue this for 15-18 minutes until the rice grains are soft but with a firm bite.

4. With the last two ladles of stock, add the mussels. Remove from the heat and add the parmesan, remaining butter, some salt and pepper and the chopped parsley. Check the seasoning, rest the risotto for a minute, then serve straight away.