Mussels in fennel broth

INGREDIENTS
1 tbsp olive oil
1 onion, finely chopped
1 fennel bulb, trimmed and finely chopped
salt and freshly ground black pepper
2 garlic cloves, grated or finely chopped
2 waxy potatoes, peeled and finely diced
300ml (10fl oz) hot vegetable stock or light fish stock
400g can coconut milk
1.35kg (3lb) fresh mussels, scrubbed and debearded
handful of basil leaves, torn

METHOD
Heat the oil in a large pan over a low heat. Add the onion, fennel, and a pinch of salt, then sweat for about 5 minutes until softened. Add the garlic and potatoes, and cook for a few minutes more, being careful not to allow the mixture to brown at all.
Pour in the stock, and bring to the boil. Add the coconut milk, reduce the heat slightly, and simmer gently for about 10 minutes, or until the potatoes are cooked. Bring back to the boil, add the mussels, and put a lid on the pan. Cook for about 5 minutes, until all the mussels are open (discard any that do not).
To serve, stir through the basil, taste the broth, and season if needed. Serve immediately.