Infuse ¼ cup (60 grams) of finely chopped shallots in a mixture of ½ cup (125 milliliters) of white wine and ½ cup (125 milliliters) of white wine vinegar. Reduce the mixture by three-quarters. Add 2 cups (500 milliliters) of reduced-cream white sauce to the infusion, reduce if necessary, and finish the sauce with 3 ounces (90 grams) of butter or shallot butter. Adjust the seasonings. Straining is optional.