Pour 60 ml
dry white wine and 40 ml white (spirit) vinegar into a
saucepan on medium heat. Salt and pepper, then add the chopped shallot.
Bring to the boil and leave to reduce gently by 3/4, until very little liquid is left.
You can add 2 tablespoons
liquid cream at this stage, which is not essential, but - apparently - this is the secret of a successful beurre blanc.