1. Grease a 9×13-inch baking dish.
2. Make French toast:
3. When ready to bake, remove French toast from the refrigerator and discard plastic wrap. Preheat the oven to 4500F.
4. Make topping:
5. Bake in oven uncovered until casserole is browned and bubbling, about 30 minutes. Cover with aluminum foil if the top is browning too much.
6. To serve, cut into squares and place upside down onto plates.