Preparation Lightly oil a shallow 8-inch square baking dish or pan and line bottom and sides with a sheet of plastic wrap. Bring Sauternes and sugar to a boil in a small heavy saucepan, stirring until sugar has dissolved. Meanwhile, sprinkle gelatin over water in a small bowl and let soften 1 minute. Pour hot wine over gelatin mixture, then stir until gelatin has dissolved. Cool to room temperature. Pour wine-gelatin mixture into lined dish and chill, covered, until set, at least 4 hours. Lift gelée out of dish using plastic wrap and transfer to a cutting board. Cut gelée into 3/4-inch squares (without cutting through plastic). Cut foie gras into 1-inch squares (about 1/4 inch thick). Transfer squares with offset spatula to a tray lined with plastic wrap, then top each with a square of gelée (you will have extra gelée). Chill, covered with plastic wrap, until ready to serve. Preheat oven to 450°F with rack in upper third. Trim crusts from bread, then brush with butter and cut 6 (1 1/4-inch) squares from each slice. Arrange in a 4-sided sheet pan and bake until golden, about 6 minutes. Top toasts with foie-gras-and-gelée stacks. Cooks’ notes:•Gelée can be chilled up to 2 days. •Foie-gras-and-gelée stacks can be chilled up to 1 day. •Bread can be buttered and cut (but not baked) 2 hours ahead and chilled, covered with plastic wrap.