Trim the livers to remove any green bile, fat, and sinews. Soak them in the milk in the refrigerator for at least 3 hours. Drain the livers and rinse under cold running water until the water runs clear; pat dry.
Marinate the livers in the Armagnac seasoned with ¼ teaspoon salt and ⅛ teaspoon pepper for 1 to 2 hours.