1. Butter a 9-by-13-inch baking dish. Arrange bread in a tight, flat layer in dish.
2. In a large bowl, whisk eggs with milk, sugar and vanilla until blended; pour over bread. Arrange peaches on top and sprinkle with brown sugar and cinnamon. Cover tightly and refrigerate for at least 8 hours.
3. Remove baking dish from refrigerator 30 minutes before baking. Preheat oven to 350°F. Pour cream into a small pan; bring to a boil over high heat. Cook until reduced by half, about 10 minutes. Drizzle over peaches and bake, uncovered, until casserole is lightly browned on top and just cooked through, 45 to 55 minutes. Let stand for 10 minutes before serving.