Béarnaise sauce

Method

1. First clarify the butter. Put it in a small saucepan over low heat. When the milky sediment rises to the top, either skim off the sediment with a spoon or pour the butter through a small muslin-lined sieve set over a bowl.

2. Put the vinegar, 2 tablespoons of the tarragon, the shallot and crushed peppercorns in a small, heavy-based saucepan. Simmer gently until reduced by half.
Remove from the heat and allow to cool.

3. Add the egg yolks and cold water to the vinegar mixture. Set the pan over low heat and whisk continuously for about 10 minutes until the sauce emulsifies. Do not allow it to reach boiling point.

4. Remove the pan from the heat. Whisk in the clarified butter a little at a time. Season to taste, then push the sauce through a fine sieve.

5. Stir in the remaining tablespoon of tarragon, the chervil and lemon juice to taste. Serve immediately.