- Boil the vinegar with pepper, bay leaf and mace until the quantity of liquid is reduced to 1 tbsp. In a glass bowl mix egg yolks with salt and a piece of butter. Place it over the saucepan with boiling water and whisk until it thickens. However, make sure that it does not boil.
- Pass the reduced vinegar through a sieve and add to the egg mix constantly stirring. Add butter piece by piece.
- When the sauce thickens, remove it from the heat and whist for 1 min. Add lemon juice and salt (if needed). Keep the sauce warm until serving.