Sauce Lyonnaise (Onion Sauce)

Ingredients

• 3 medium onions
• butter
• 2 décilitres white wine
• 2 décilitres vinegar
• three quarters of a litre sauce Demi-glace

Instructions

1. Colour 3 medium chopped onions lightly in butter, very gently, so that they are almost completely cooked.
2. Moisten with 2 décilitres of white wine and 2 décilitres of vinegar, and reduce by two thirds.
3. Add three quarters of a litre of sauce Demi-glace.
4. Let it boil very gently for 5 to 6 minutes.
5. Pass through the étamine.