Combine all the ingredients in a medium nonreactive bowl. Set up a double boiler, adding 3 inches of water to the bottom pot. Bring to the boil. Whisk the ingredients until frothy. Pour into the double boiler and continue to whisk until the sauce is lightly thickened, about 7 minutes. If the sauce seems to be thickening too rapidly, lift the top pot off the heat, whisking continuously to disperse heat. Return the pan to the double boiler and continue whisking until done.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.