Béarnaise Sauce

1. 1

   Melt 1 tablespoon butter in a small saucepan over medium heat. Add shallots and a pinch of salt and pepper; stir to coat. Stir in vinegar, reduce heat to medium-low, and cook until vinegar is evaporated, 3-4 minutes. Reduce heat to low and continue cooking shallots, stirring frequently, until tender and translucent, about 5 minutes longer. Transfer shallot reduction to a small bowl and let cool completely.

2. 2

   Meanwhile, fill a blender with hot water to warm it; set aside. Melt remaining 1 cup butter in a small saucepan over medium heat until butter is foamy. Transfer butter to a measuring cup.

3. 3

   Drain blender and dry well. Combine egg yolks, lemon juice, and 1 tablespoon water in warm, dry blender. Puree mixture until smooth. Remove lid insert. With blender running, slowly pour in hot butter in a thin stream of droplets, discarding milk solids at bottom of measuring cup. Continue blending until a smooth, creamy sauce forms, 2-3 minutes. Pour sauce into a medium bowl. Stir in shallot reduction and tarragon and season to taste with salt, pepper, and more lemon juice, if desired. DO AHEAD:

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