Mornay Sauce

Ingredients

• 1 liter béchamel sauce (mother sauce)
• 2 decilitres cooking liquid from the fish it is destined for
• 50 grams Gruyère cheese, grated
• 50 grams Parmesan cheese, grated
• 100 grams butter

Instructions

1. Add 2 decilitres of the fish cooking liquid to 1 litre of béchamel sauce (mother sauce) and reduce by a good third.
2. Stir in the grated Gruyère and Parmesan cheeses. Continue stirring over the heat for a few seconds to ensure the cheese melts completely.
3. Finish the sauce by incorporating the butter, stirring to combine fully. Taste and adjust seasoning as needed.