1/4 cup white wine vinegar1/4 cup fresh lemon juice1 tablespoon minced shallots1/4 teaspoon salt1/8 teaspoon freshly ground pepper12 ounces (1 1/4 cups) butter, chilled and cut into piecesA squeeze of fresh lemon juice
In a heavy saucepan, boil first 5 ingredients until mixture is reduced to about 1 1/2 tablespoons. Remove from heat
Immediately beat in half the butter, until it forms a creamy paste.
Set saucepan over low heat and continue beating in a piece of butter at a time just as the previous piece is almost fully incorporated. The sauce should have the consistency of a light hollandaise.
Remove from heat, season to taste with salt, pepper and a squeeze of lemon.
Makes 2 cups of sauce.
Here is another I've also tried and like:
Ingredients:
1 cup dry white wine
½ cup white wine vinegar
1 Tbsp finely chopped shallot
1 lb unsalted butter, cold
Kosher salt, to taste
Method:
Heat wine, vinegar and shallots in a saucepan until the liquid boils, then lower the heat a bit and continue simmering until the liquid has reduced down to about 2 tablespoons. This should take about 10 minutes.
While the liquid reduces you can cut the butter into medium (½-inch) cubes, but either leave this until the reduction is nearly finished or return the butter cubes to the refrigerator to keep them cold while the liquid finishes reducing.
Once the wine-vinegar mixture has reduced to 2 tablespoons, reduce the heat to low and start adding the cubes of butter, one or two at a time, and whisk rapidly with a wire whisk.
As the butter melts and incorporates, add more butter and keep whisking. Continue until you only have 2-3 cubes remaining. Remove from heat while whisking in the last few cubes, and whisk for a moment or two more. The finished sauce should be thick and smooth.
Season to taste with Kosher salt. Traditionally the shallots would be strained out before serving, but doing so is optional. Serve right away.