Béarnaise Sauce

Method

1. 1Finely dice the shallot. Roughly chop most of the fresh tarragon, reserving a teaspoon of finely chopped leaves for finishing. Crush the black peppercorns lightly with the side of a knife.
2. 2Make the reduction: combine the diced shallot, chopped tarragon stems and leaves, crushed peppercorns, and white wine vinegar in a small saucepan. Bring to a simmer over medium heat and reduce until only about 1 tablespoon of liquid remains — this takes roughly 3–4 minutes. Strain through a fine sieve into a heatproof bowl, pressing the solids to extract all the flavor. Discard the solids.
3. 3Melt the butter in a small saucepan over low heat until completely liquid. Do not let it brown. Remove from heat and let it cool for 2 minutes — it should be warm but not hot enough to scramble the yolks.
4. 4Add the egg yolks to the strained reduction in the heatproof bowl. Set the bowl over a pot of barely simmering water — the bowl should not touch the water. Whisk the yolks constantly for 2–3 minutes until they thicken and turn pale, and the whisk leaves visible trails in the mixture.
5. 5Remove the bowl from the heat. While whisking continuously, add the melted butter in a very slow, thin stream — just a few drops at first, then a thin trickle as the emulsion builds. If the sauce gets too thick, add a few drops of warm water. Continue until all the butter is incorporated and the sauce is thick, creamy, and glossy.
6. 6Stir in the reserved finely chopped fresh tarragon. Taste and adjust with a pinch of salt and a squeeze of lemon juice if needed. Serve immediately — béarnaise does not reheat well. If it must wait, keep the bowl over warm (not hot) water for up to 20 minutes.