2. Drain the raisins, reserving the liquid. Discard the vanilla bean. Put the liquid back in the saucepan and bring to a boil. Reduce to about 1/3 cup, or until the syrup turns a deep golden color, 10 to 15 minutes. Watch carefully so the syrup doesn't burn. If it starts to foam, remove from heat immediately. The syrup will continue to thicken as it cools, and have a texture similar to light maple syrup. Cool completely.
3. Preheat the oven to 400 F.
4. Brush butter onto both sides of the bread slices. Bake for 8 to 10 minutes or until golden brown. Let cool completely.
5. To assemble: Put a slice of cheese on each toast. Sprinkle with a few raisins and drizzle syrup over the top.
Note: If you have any raisins and syrup left over, combine them and refrigerate in an airtight container. They will keep for 2 weeks.
Andrea Reusing is the creator of the restaurant Lantern in Chapel Hill, N.C., and author of the book Cooking in the Moment: A Year of Seasonal Recipes. In this installment of The Key 3, she shares with Lynne Rossetto Kasper the techniques behind three of her favorite recipes: Turnip Soup, Overnight Braised Short Ribs and Tomato Salad.