trimmed and finely chopped
preferably Caerphilly, grated
crusty, cubed, for serving
Put butter into a saucepan and melt over a low heat.
Add leeks, cover pan and cook gently for 10 minutes until tender.
Stir in flour and cook for 1 minutes, then add lager and heat until thickened, stirring all the time.
Gradually add cheese and continue to cook until melted, stirring frequently.
Season with pepper.
Pour into a fondue pot and serve with cubes of crusty bread.