Preheat your oven to 350°F (175°C).
In a large mixing bowl, whisk together the eggs, milk, heavy cream, granulated sugar, vanilla extract, ground cinnamon, and salt until well combined.
Place the bread cubes into a greased 9x13-inch baking dish. Pour the egg mixture evenly over the bread cubes, ensuring all pieces are soaked. Press down gently on the bread to help it absorb the liquid.
Cover the baking dish with plastic wrap and refrigerate for at least 30 minutes to allow the bread to soak up the mixture (you can also let it sit overnight).
Remove the casserole from the refrigerator and allow it to sit at room temperature for about 10 minutes before baking.
Bake in the preheated oven for 40-45 minutes, or until the top is golden brown and the center is set. If desired, you can cover loosely with aluminum foil for the first 20 minutes to prevent over-browning.
Let the casserole cool for a few minutes before slicing and serving.