
Make the caramel base: In a saucepan over medium heat, melt ½ cup unsalted butter, 1 cup packed brown sugar, and 2 tablespoons light corn syrup. Stir until the mixture is smooth and bubbling. Once ready, pour this caramel into the bottom of a 9x13-inch baking dish, spreading evenly.
Layer the bread: Take 1 loaf of challah or brioche bread, sliced and arrange the slices in the baking dish on top of the caramel layer, overlapping them slightly.
Prepare the custard mixture: In a large bowl, whisk together 6 large eggs, 2 cups whole milk, 1 cup heavy cream, 1 tsp vanilla extract, ½ tsp ground cinnamon (optional), and ¼ tsp salt. Mix until fully combined.
Soak the bread: Pour the custard mixture evenly over the arranged bread slices, ensuring each slice is well-covered. You may gently press the bread down to help it absorb the custard.
Cover and refrigerate: Wrap the dish tightly with plastic wrap and place it in the refrigerator overnight. This allows the bread to soak up all the flavors.
Preheat the oven: Set your oven to 350°F (175°C) and let it heat up.
Bake the French toast: Remove the plastic wrap from the baking dish and bake the French toast uncovered for 40-45 minutes or until it’s golden brown and slightly puffed up.
Caramelize the topping: Once baked, sprinkle ½ cup granulated sugar evenly over the top and use a kitchen torch to caramelize the sugar until it forms a nice crust. Alternatively, place it under a broiler for 1-2 minutes, watching closely to prevent burning.
Cool before serving: Let the French toast cool for about 5 minutes before slicing and serving. This brief cooling helps the caramel harden a bit more.
Garnish: Top with fresh berries, a dusting of powdered sugar, or a dollop of whipped cream before serving!