Whisk the eggs, milk, heavy cream, melted butter, cinnamon and salt in a large bowl.
Pour 1 cup maple syrup into the bottom of a 9-by-13-inch baking dish. Place the bread slices on top of the maple syrup, shingling them in the pan. Pour the egg mixture on top. Cover tightly with plastic wrap and refrigerate overnight.
Preheat the oven to 350˚. Uncover the French toast and bake until puffed, golden brown and cooked through, about 1 hour. Let rest for 10 minutes before serving.
Take your casserole out of the fridge and let it sit at room temperature while the oven preheats.