Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish with butter or non-stick spray. Cut the bread into roughly 1- to 1.5-inch cubes and spread evenly in the dish.

In a large bowl, whisk together eggs, milk, heavy cream, granulated sugar, brown sugar, vanilla extract, cinnamon, and salt until smooth. Pour the mixture evenly over the bread, pressing lightly so each cube absorbs custard.

Cover the casserole and refrigerate for at least 1 hour or overnight for a soft, custardy interior.

In a small bowl, combine melted butter with chopped pecans or walnuts and set aside.

Remove the casserole from the refrigerator. Drizzle caramel sauce over the top, then sprinkle the buttered nuts evenly across the casserole.

Bake in the preheated oven for 45–50 minutes, or until the top is golden brown and custard is set. A knife inserted in the center should come out clean.

Let the casserole cool for 5–10 minutes to allow the caramel to set slightly.

Slice into portions and garnish with powdered sugar if desired. Serve warm, with extra caramel drizzle or fresh fruit on the side.