Step 1

Prepare the reduction – In a small saucepan, combine vinegar, white wine, shallots, and half of the tarragon. Simmer over low heat until the liquid is reduced to about 1 tablespoon. Strain and let cool slightly.

Step 2

Whisk the egg yolks – In a heatproof bowl, whisk the egg yolks with the reduction until slightly thickened.

Step 3

Create a double boiler – Place the bowl over a saucepan of gently simmering water (without touching the water). Continue whisking until the mixture thickens and becomes pale.

Step 4

Incorporate the butter – Slowly drizzle in the melted butter while whisking continuously until the sauce emulsifies into a smooth, velvety consistency.

Step 5

Season and finish – Stir in the remaining tarragon, salt, pepper, and a squeeze of lemon juice if desired. Serve immediately.