2 leeks (approximately 350g/12oz), finely sliced
fresh green salad, to serve
125驳/4陆辞锄 plain flour
1 tsp wholegrain mustard
freshly ground black pepper
30g/1oz unsalted butter, melted
50驳/1戮辞锄 butter
100驳/3陆辞锄 Caerphilly cheese, finely grated
50ml/2fl oz double cream
1 large free-range egg
300ml/10fl oz semi-skimmed milk
75ml/2陆fl oz dry white wine or vegetable stock