Melt ½ cup of unsalted butter in a saucepan over low heat. Stir in 1 cup of packed brown sugar and ¼ cup of light corn syrup until smooth and bubbling.

Pour the caramel into a greased 9x13-inch baking dish and spread evenly.

Cut French bread or brioche into 1-inch thick slices and layer over the caramel in the baking dish.

In a bowl, whisk together 4 large eggs and gradually add 2 cups of half-and-half, 2 teaspoons of vanilla extract, ½ teaspoon of salt, and optionally 1 teaspoon of cinnamon.

Pour the custard mixture over the arranged bread, ensuring every slice is soaked.

Cover tightly with plastic wrap and refrigerate for at least 6 hours, preferably overnight.

Preheat oven to 350°F, let the dish sit at room temperature for 20 minutes, then bake uncovered for 35-40 minutes until golden brown.

After baking, let it rest for 5 minutes, then flip it onto a serving platter, dust with powdered sugar and serve with fresh berries if desired.