Lightly grease a 9x13 baking dish. Evenly layer the slices of bread in the dish.
Whisk together the eggs, milk, cream, vanilla, and ground cinnamon. Pour mixture over the bread slices, ensuring that every piece gets moistened. Cover and chill overnight.
Optional: place the butter, brown sugar, and corn syrup in a bowl. Cover and set aside until morning.
Preheat the oven to 350ºF.
Optional: Microwave the butter, sugar, and corn syrup for about 45 seconds (or until butter is melted). Mix together and spread over the (unbaked) French toast.
Bake uncovered for 40 minutes.
Let rest for about 10 minutes before serving warm!
