In a saucepan, combine the dry white wine, white wine vinegar, shallot, and tarragon leaves. Simmer until reduced to about 2 tablespoons.

Strain the mixture into a bowl and let it cool slightly.

Whisk in the egg yolks and lemon juice until combined.

Place the bowl over a pot of simmering water (double boiler) and whisk continuously until the mixture thickens.

Slowly drizzle in the melted butter while whisking until emulsified.

Stir in the chopped tarragon and season with kosher salt to taste.