01 - Melt butter in a small saucepan over medium heat. Add brown sugar and corn syrup, stirring constantly until smooth and bubbling. Pour evenly into a 9x13-inch baking dish.
02 - Place bread slices in a single layer over the caramel, arranging them tightly with slight overlap to fit the dish.
03 - Whisk together eggs, whole milk, heavy cream, granulated sugar, vanilla extract, and salt in a large mixing bowl until completely smooth and combined.
04 - Evenly pour the custard mixture over the bread. Gently press down on each slice to ensure thorough absorption of the liquid.
05 - Cover the dish tightly with plastic wrap. Refrigerate for 8 to 12 hours to allow the bread to fully soak up the custard.
06 - Preheat oven to 350°F. Remove the dish from the refrigerator and let it sit at room temperature while the oven heats, approximately 15 to 20 minutes.
07 - Bake uncovered for 30 to 35 minutes until the top is puffed and golden brown, and the custard is completely set with no liquid remaining.
08 - Remove from oven and let rest for 5 minutes to allow the dish to settle slightly.
09 - Sprinkle granulated sugar evenly over the entire surface. Using a kitchen torch, melt and caramelize the sugar until dark golden and bubbly. Alternatively, place under the broiler for 1 to 2 minutes, watching closely to prevent burning.
10 - Invert portions onto plates or serve directly from the dish, spooning any remaining caramel sauce from the bottom over each slice.