Metric:
300ml Milk
4 Eggs
100gr Strong Gruyère
( finely grated... or Cheddar )
50gr Butter
( plus extra for greasing )
50gr Flour
50gr Parmesan
( finely grated )
25gr Breadcrumbs
3gr Mustard Powder
Pinch of Salt,Cayenne Pepper and Nutmeg