1/4 cup white wine
1/4 cup white wine vinegar
1 tablespoon minced shallots
1/4 teaspoon salt
1/4 teaspoon white pepper
1/4 pound chilled unsalted butter, cut into cubes
Combine the white wine, white wine vinegar, shallots, salt and pepper
in a small heavy skillet. Bring the liquid to a boil, then lower it to
a simmer. Cook the reduction until approximately 1 tablespoon of the original
amount of liquid remains.
With the skillet still over the heat, add the cubes of butter a couple
of pieces at a time. Shake and stir the pan constantly while the butter
is being added to encourage emulsification. As the pieces melt and emulsify
into the sauce, add another piece or two until all of the butter has been
added.
When the last piece(s) of butter have been added to the sauce, and are
almost melted, remove the pan from the heat. Continue to stir and shake
the pan until all of the butter has been incorporated into the sauce. If
desired, strain the sauce through a fine mesh or muslin colander and serve
at once.