• 2 ounces dry white wine
• 2 ounces white-wine vinegar
• 2 tablespoons finely chopped shallot
• 1/3 cup heavy cream
• 1/4 teaspoon salt
• 1/8 teaspoon white pepper, or to taste
• 2 sticks (1 cup) unsalted butter, cut into tablespoon-size pieces and chilled

• Boil wine, vinegar, and shallot in a 2- to 3-quart heavy saucepan over moderate heat until liquid is syrupy and reduced to 2 to 3 tablespoons, about 5 minutes.
• Add cream, salt, and white pepper and boil 1 minute.
• Reduce heat to moderately low and add a few tablespoons butter, whisking constantly.
• Add remaining butter a few pieces at a time, whisking constantly and adding new pieces before previous ones have completely liquefied (the sauce should maintain consistency of hollandaise), lifting pan from heat occasionally to cool mixture.

• Remove from heat, then season to taste with salt and pepper
• Pour sauce through a medium-mesh sieve into a sauce-boat, pressing on and then discarding shallot.
• Serve immediately.

Wine mixture can be reduced, and cream and seasoning added, up to 1 hour ahead. Boil cream 1 minute before adding butter.