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