White wine butter sauce (Beurre blanc)

1. Cut the butter into cubes and keep it cold until use (cold butter is key to the emulsion).

2. Put the finely chopped shallot into a saucepan with the dry white wine and the white wine vinegar.

3. Boil over low heat until the liquid has almost completely evaporated and a syrupy reduction remains.

4. Reduce the heat to minimum and whisk in the cold butter cubes one at a time, stirring constantly.

5. Make sure the sauce does not boil (it would split) – only warm it until it becomes a silky, glossy emulsion.

6. Season with salt and pepper, strain if you like, and serve at once, lukewarm (with fish, seafood).

Tip: Beurre blanc is an emulsion of cold butter and an acidic reduction – the secret is a constant, low temperature. Don't let it boil, and work the butter in patiently, bit by bit, so it stays creamy.