Making your own is very easy.
- 2 tblsp white wine vinegar
- 225g (8oz) unsalted butter, diced and chilled
- 3 egg yolks
- Sea salt and freshly ground black pepper
- Place the white wine vinegar in a small pan with 1 tablespoon water and reduce to 1 tablespoon. Leave to cool.
- Melt the butter in a small pan or in a dish in the microwave. Set aside and keep warm.
- Beat 2 tablespoons water into the egg yolks, then beat into the reduced vinegar mixture. Stir with a whisk over a low heat until smooth and velvety, beating continuously.
- Add the melted butter to the egg yolk mixture, little by little, until you have achieved a thick, smooth sauce. If it becomes too thick, add 1 tablespoon warm water. Season to taste and keep warm but not hot or the sauce will split.