01 - Melt butter with brown sugar and corn syrup in a small saucepan over medium heat, stirring constantly until smooth and bubbling. Pour mixture into the bottom of a 9x13-inch baking dish and spread evenly.
02 - Place bread slices in a single layer over the caramel, slightly overlapping if necessary to fit the dish.
03 - Whisk together eggs, milk, cream, granulated sugar, vanilla extract, and salt in a mixing bowl until completely smooth and combined.
04 - Pour custard mixture evenly over the bread slices. Gently press down on bread to help it absorb the liquid.
05 - Cover dish tightly with plastic wrap and refrigerate for 8 to 12 hours to allow bread to fully absorb the custard.
06 - Remove dish from refrigerator and let sit at room temperature while oven preheats to 350°F.
07 - Bake uncovered for 30 to 35 minutes until puffed, golden brown, and the custard is completely set.
08 - Let the dish rest for 5 minutes after removing from the oven.
09 - Sprinkle granulated sugar evenly over the surface. Use a kitchen torch to melt and caramelize the sugar until golden and crispy. Alternatively, place under the broiler for 1 to 2 minutes, watching closely to prevent burning.
10 - Serve warm, spooning any extra caramel sauce from the bottom of the dish over each portion.