Béarnaise

Béarnaise is a rich, warm sauce made from egg yolks and melted butter, flavored with a sharp reduction of vinegar, white wine, shallot and tarragon. It is a close relative of hollandaise, which uses lemon instead of the herb reduction. It is best known as the sauce for steak and fries.

How to do it

1. In a small pan, simmer 60 ml (1/4 cup) white wine vinegar, 60 ml (1/4 cup) dry white wine, 1 finely chopped shallot, a few crushed peppercorns and 1 tablespoon chopped tarragon until about 2 tablespoons of liquid remain. This is the reduction. Strain it and let it cool slightly.
2. Put 3 egg yolks and the reduction in a heatproof bowl over a pan of barely simmering water, a bain-marie.
3. Whisk until the yolks are pale, thick and hold a trail, about 2 to 4 minutes.
4. Off the heat, whisk in 175 g (3/4 cup) of warm melted or clarified butter, a little at a time.
5. Stir in fresh chopped tarragon and a little chervil if you have it. Season with salt.

How to tell it is done

The sauce is thick enough to coat a spoon, smooth and glossy, and holds its shape briefly when dropped on a plate. It should be warm, not hot.

Why it works

The yolks hold small drops of butter in the watery reduction, forming an emulsion. Gentle heat thickens the yolk proteins so the sauce has body. Too much heat scrambles them.

Common mistakes

• Heating the yolks too hard. Once they pass about 70°C (160°F) they start to scramble, and the sauce turns grainy.
• Adding butter too fast, which makes the sauce split. If it does, whisk a fresh yolk with a spoon of warm water and slowly whisk the broken sauce into it.
• Letting it sit over heat. Keep it warm in a bowl over warm, not simmering, water and use it within an hour.
• Skipping the reduction. Without it the sauce tastes flat.

In recipes

"Sauce béarnaise" or "béarnaise" on a steak recipe means this sauce. "Choron sauce" is béarnaise with tomato added.