Red Snapper with Sherry Beurre Blanc

Ingredients

1/4 cup medium-dry Sherry
1 large shallot, minced (about 1/4 cup)
2 tablespoons dry white wine, or water
1 tablespoon Sherry vinegar, (available at specialty foods shops and some supermarkets) or white-wine vinegar
3 tablespoons cold unsalted butter, cut into 4 pieces
10 ounces total), seasoned with salt and pepper

Directions

In a small saucepan cook the Sherry, the shallot, the white wine, the vinegar, and salt and pepper to taste over moderately high heat until the liquid is reduced to about 2 tablespoons, remove the pan from the heat, and whisk in the butter, 1 piece at a time, adding each new piece before the previous one has melted completely.
(The sauce should not get hot enough to liquefy.
It should be the consistency of thin hollandaise.
) On a foil-covered broiler pan broil the fillets under a preheated broiler about 4 inches from the heat for 4 to 5 minutes, or until they just flake, divide them between 2 plates, and spoon the sauce over them.