François Pierre La Varenne in 1651 describes a a sauce : "avec du bon beurre frais, un peu de vinaigre, sel et muscade, et un jaune d’œuf pour lier la sauce" "make a sauce with good fresh butter, a little vinegar, salt, and nutmeg, and an egg yolk to bind the sauce; take care that it doesn't curdle...".
125 g butter
3 egg yolks
2 tablespoon white wine
1 tablespoon lemon juice
Melt butter and remove the whey. In a pot bring water to boil and in another bowl add egg yolks, wine and 1 pinch of salt. Over steam beat egg yolks until it gets thick and foamy. Add butter in thin spurt and keep on whisking. Season with salt, pepper and lemon juice.