Instructions: Combine vinegar, wine, shallots, black pepper, and 1 1/2 teaspoons tarragon in a small saucepan. Cook over medium heat until reduced to 1 tablespoon, 5 to 10 minutes.

Add egg yolks and 1 tablespoon water to reduced vinegar mixture. Whisk until thick and pale, about 2 minutes. Set pan over moderately-low heat, and continue to whisk at reasonable speed, reaching all over bottom and insides of pan, where eggs tend to overcook. To moderate heat, frequently move pan off burner for a few seconds, then back on. As they cook, the eggs will become frothy and increase in volume, then thicken. When the bottom of the pan is visible in the streaks left by the whisk, and the eggs are thick and smooth, remove pan from heat.

By spoonfuls, add soft butter, whisking constantly to incorporate each addition. As the emulsion forms, add butter in slightly larger amounts, always whisking until fully absorbed. Continue incorporating butter until sauce has thickened to desired consistency. Season with salt, remaining 1 1/2 teaspoons chopped tarragon and, if desired, pepper. Add a few drops of lemon juice if necessary.

This recipe yields about 1 cup.

Yield: 1 cup

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