Preheat the oven to 350°F (175°C).

Grease a 9x13-inch baking dish with butter or nonstick spray.

Cut the loaf into 1-inch cubes and spread them evenly in the dish.

In a medium bowl, whisk the eggs until smooth.

Add milk, heavy cream, sugar, vanilla, cinnamon, and salt. Whisk until well combined.

Pour the custard evenly over the bread cubes.

Press down gently with a spatula or your hands so the bread soaks up the mixture.

Cover the dish tightly and refrigerate at least 2 hours or overnight for best flavor and texture.

After chilling, remove the cover and bake for 45 to 50 minutes. The top should be golden and a knife inserted in the center should come out mostly clean.

Let the casserole rest for 5 minutes, then slice and serve warm with syrup, fresh berries, or a dusting of powdered sugar.