Preheat your oven to 350°F (175°C).
Grease a 9x13-inch baking dish with butter or cooking spray.
Cut the bread into cubes and place them evenly in the baking dish.
In a large mixing bowl, whisk together the eggs, milk, heavy cream, sugar, vanilla, cinnamon, nutmeg, and salt.
Pour the egg mixture evenly over the bread cubes, ensuring all pieces are soaked.
Cover the dish with plastic wrap and refrigerate for at least 1 hour, or preferably overnight.
Remove the dish from the refrigerator and let it sit at room temperature for 15 minutes.
Bake in the preheated oven for 45 minutes, or until the top is golden brown and the center is set.
Let cool for a few minutes before serving.
Top with fresh berries and a dusting of powdered sugar if desired.