This unusual sauce is an excellent accompaniment to fish. It is based on an infusion of chopped onions, carrots, and celery (a mirepoix) and white wine, which is then combined with egg yolks and finished with crustacean butter and (optionally) anchovy paste.
Gently stew ½ cup (125 milliliters) mirepoix in ½ ounce (15 grams) butter. Do not let the mirepoix brown. When the mirepoix is cooked, after about 10 minutes, add 1 cup (250 milliliters) white wine and 1 cup (250 milliliters) fresh fish stock. Gently reduce this mixture until only 3 tablespoons (45 milliliters) syrupy glaze remain in the saucepan. Add 1 tablespoon (15 milliliters) Madeira and cook for 1 minute more to remove the alcohol from the Madeira. Strain this mixture through a fine-mesh strainer, let it cool, and combine it with 2 egg yolks. Whip this mixture into a sabayon and finish it with ½ cup (125 milliliters) clarified butter and 1 ounce (30 grams) Crustacean Butter. Traditionally, 1 teaspoon (5 milliliters) anchovy paste is called for, but for some, it detracts from the sauce.