1. Place butter in a small saucepan over medium-low heat; cook 5 minutes or until completely melted. Carefully skim solids off the top with a spoon; discard solids. Slowly pour remaining butter out of pan, leaving remaining solids in pan; discard solids.
2. Combine egg yolks and 2 tablespoons water in a small saucepan, stirring with a whisk until foamy. Place pan over medium heat, stirring constantly until mixture thickens slightly. Gradually add 1/4 cup clarified butter, about 1 tablespoon at a time, stirring with a whisk until each addition is incorporated and mixture is thick. Reserve remaining clarified butter for another use.
3. Stir juice and salt into butter mixture, whisking until blended.
Béarnaise Sauce: Prepare recipe through step 2. Omit juice. Combine 3 tablespoons dry white wine, 3 tablespoons white wine vinegar, 1 1/2 tablespoons minced shallots, and 3 tarragon sprigs in a heavy saucepan; bring to a simmer. Cook until reduced to 2 tablespoons. Strain through a sieve into butter mixture. Stir in salt, 1/8 teaspoon black pepper, and 1/2 teaspoon chopped fresh tarragon. Yield: about 2/3 cup (serving size: about 1 tablespoon).
Calories 63; Fat 6.5g (sat 3.9g, mono 0.4g, poly 0.1g); Protein 0.5g; Carb 0.2g; Fiber 0g; Chol 57mg; Iron 0.1mg; Sodium 32mg; Calc 5mg