Fish Gratin

Yield:	4 servings
Categories:

750	g	White fish fillets; (such as cod or
		; haddock)
		Salt and pepper
1	tb	Lemon juice
45	g	Butter
25	g	Flour
300	ml	Milk
150	ml	Single cream
100	g	Cooked shrimps or prawns; (shelled weight)
		; roughly chopped,
		; optional)
2		Egg yolks
50	g	Parmesan or other full-flavoured hard; freshly grated
		; cheese