Make a white
sauce: Melt the
butter in a saucepan and add the
flour, stirring with a wire whisk. Add the
milk, stirring rapidly with whisk. When blended and smooth, add the
salt,
pepper,
nutmeg. Simmer gently for 5 minutes stirring the bottom regularly to ensure it doesn't burn. Remove
sauce from heat and whisk in
egg yolks, herbs and
trout fillet.
Sauce should be thick and creamy.