1/2 cup white wine vinegar
2 Tbs. minced shallot
2 tsp. plus 1 Tbs. chopped fresh tarragon
2 Tbs. water
4 egg yolks
1 cup clarified butter, warmed
1/2 tsp. fresh lemon juice, plus more, to taste
Salt and freshly ground white pepper, to taste
In a small saucepan over medium-high heat, combine the vinegar, shallot and the 2 tsp. tarragon. Bring to a boil, reduce the heat to low and simmer until the vinegar is almost completely evaporated, 3 to 5 minutes. Remove from the heat and let cool slightly, then strain into a heatproof bowl. Add the water and egg yolks. Set the bowl over but not touching simmering water in a small saucepan and whisk until thick and pale yellow, about 3 minutes.
Transfer the mixture to a blender and blend until smooth. Let cool for 1 minute. With the motor running, slowly pour in the clarified butter and blend until incorporated. Add the 1/2 tsp. lemon juice, or to taste, and the 1 Tbs. tarragon. Season with salt and white pepper and process to combine. Transfer the sauce to a double boiler and keep warm over very low heat until ready to serve.
Makes about 2 cups.