An easy recipe for the classic French Sauce Béarnaise, inspired by the creator in the 1830s near Paris, in Saint-Germain-en-Laye.
Bring the white vinegar, wine, shallots, tarragon branches and pepper to a boil in a small saucepan. As soon as it boils, reduce the heat and leave to reduce for about 5 minutes until there's about a couple of tablespoons. Pour into another bowl and set aside to cool then filter out the shallots and herbs using a sieve.
Fill the saucepan with 1/4 of water and bring to a simmer. Place over it a large bowl with the cooled vinegar reduction, yolks and water then whisk constantly until the sabayon becomes mousse-like.
After about 5 minutes, as soon as the sauce starts to thicken, take the bowl off the heat and, continuing to whisk, incorporate the warm, melted butter. Add the chopped tarragon, chervil and parsley, if using. Season with a little salt and it's ready to serve.
If not serving straight away, keep at room temperature and return the bowl over the simmering water before ready to serve to re-heat, adding a little hot water if necessary.