Mussels with cider, leeks and bacon - River Cottage

Ingredients

• 1kg mussels
• A small knob of butter
• 1-2 tablespoons rapeseed, olive or sunflower oil
• 100g unsmoked streaky bacon or pancetta, chopped
• 1 large or 2 medium leeks, finely sliced
• 1 teaspoon thyme leaves
• 1 bay leaf
• 250ml medium-sweet cider
• 1 teaspoon wholegrain mustard
• 2-3 tablespoons double cream
• Sea salt and freshly ground black pepper
• Lots of chopped parsley, to serve