1 heaped tbsp chopped chives, plus extra for garnish
1 small onion, peeled, cut into wedges
1 tsp English mustard (or 2 tsp Dijon mustard)
40驳/1陆辞锄 plain flour
1 bay leaf
salt and freshly ground black pepper
freshly grated nutmeg, to taste
40驳/1陆辞锄 butter, plus extra for greasing
100g/3陆oz mature cheddar, coarsely grated
50g gruyere or mature cheddar, finely grated
6 tbsp double cream
3 free-range eggs, separated
275ml/10fl oz whole milk, plus extra for topping up if needed