Preparation

• Put the wine, sugar, vinegar, and 1/2 cup water in a 3-quart saucepan. Split the vanilla bean lengthwise, scrape the seeds into the pan, and add the bean. Bring to a boil, stirring until the sugar dissolves. Add the plums and adjust the heat as necessary to gently simmer, turning the plums occasionally until the skins loosen and are easily removed with tongs, 6 to 10 minutes.
• Using a slotted spoon, transfer the plums to a wide bowl, pulling off the skins with tongs as you go. Return any liquid to the pan and boil until reduced to 1 cup of syrup, about 10 minutes. Discard the vanilla bean.
• Pour the syrup over the plums, let cool to room temperature, and then refrigerate until cold, at least 2 and up to 24 hours. Serve the plums and syrup over the ice cream, sprinkled with the cookies.