Prepare the Caramel Base: In a small saucepan over medium heat, melt the butter. Add brown sugar and corn syrup, stirring until smooth and bubbling. Pour evenly into a greased 9×13-inch baking dish.

Arrange the Bread: Place the slices of brioche or challah over the caramel base in a single layer, slightly overlapping if needed.

Make the Custard: In a large bowl, whisk together the eggs, half-and-half, vanilla extract, cinnamon, and salt. Pour evenly over the bread, ensuring all slices are well soaked.

Refrigerate Overnight: Cover the dish with plastic wrap and refrigerate for at least 8 hours or overnight.

Bake: Preheat the oven to 350°F (175°C). Remove the dish from the refrigerator and let it sit at room temperature for 10 minutes. Bake uncovered for 35-40 minutes, until golden and set.

Caramelize the Topping: Let the baked French toast cool for 5 minutes. Sprinkle granulated sugar over the top. Use a kitchen torch to caramelize the sugar until golden and crisp, or place under the broiler for 2-3 minutes, watching carefully.

Serve & Enjoy: Slice and serve warm. Drizzle with maple syrup, top with fresh berries, or dust with powdered sugar.