In the morning before you prepare your overnight casserole, cut the French bread in two-inch slices, diagonally. Leave the bread out to become stale.
In the evening, butter or spray a 9x13 inch baking dish. Arrange the slices of French bread in the bottom of the baking dish.
In a large bowl, beat together eggs, half and half, vanilla, and cinnamon. Slowly pour the mixture over bread. Cover the baking dish with tin foil, and place in the refrigerator overnight.
The next morning, preheat the oven to 350 degrees. While the oven is preheating, uncover your baking dish. Put the tin foil aside (you'll reuse it later) carefully turn over each piece of soaked bread using a spatula.
In a small saucepan, combine butter, light brown sugar, and corn syrup. Stir with wooden spoon. Heat sauce until bubbling. Carefully, pour the hot sauce over the bread.
Place the tinfoil back on the baking dish, and bake for 20 minutes. After 20 minutes, remove tin foil and bake an additional 20 minutes uncovered. Allow French toast to cool slightly before eating. Top with your choice of fruit. Enjoy!
Allowing your bread time to become stale helps it retain good texture and flavor. If the bread is too moist, your french toast casserole may be somewhat mushy. You also have the option of buying day old bread at your local bakery.