Step 1: Prepare the Bread

1. Cut the Bread: Begin by cutting the challah or brioche into 1-inch cubes. You want to make sure the pieces are uniform so they cook evenly. You can use slightly stale bread for a better texture, as it will absorb the custard more effectively.
2. Butter the Baking Dish: Grease a 9×13-inch baking dish with butter or cooking spray. This ensures that the casserole doesn’t stick and allows for a golden, crispy edge.

Step 2: Make the Custard Mixture

3. Whisk Wet Ingredients: In a large mixing bowl, whisk together the eggs, whole milk, heavy cream (if using), vanilla extract, cinnamon, nutmeg, sugar, and salt. Mix until everything is well-combined, and the sugar has dissolved.
4. Add the Maple Syrup: Stir in ½ cup of maple syrup into the custard mixture for sweetness. This will ensure the casserole has that signature French toast flavor.

Step 3: Assemble the Casserole

5. Layer the Bread: Spread the cubed bread evenly in the prepared baking dish. Once the bread is in place, pour the custard mixture evenly over the bread cubes, making sure every piece is soaked with the custard. Gently press down on the bread to help it absorb the liquid.
6. Add Nuts (Optional): If you’re using nuts, sprinkle them over the top of the casserole for a crunchy texture. You can also add raisins or dried cranberries for a fruity touch if desired.
7. Cover and Rest: For best results, cover the dish with plastic wrap or aluminum foil and refrigerate it for at least 4 hours or overnight. This allows the bread to fully soak in the custard mixture and ensures that it bakes into a soft, tender casserole.

Step 4: Bake the Casserole

8. Preheat the Oven: When you’re ready to bake, preheat your oven to 350°F (175°C).
9. Bake: Remove the casserole from the fridge and uncover it. Bake for 45-50 minutes, or until the top is golden brown and slightly crispy. The custard should be set, and a knife inserted into the center should come out clean. If the top starts to brown too quickly, you can cover it loosely with foil and continue baking.
10. Rest Before Serving: Let the casserole cool for about 5 minutes before serving. This allows the custard to firm up slightly and makes it easier to slice.

Step 5: Serve and Enjoy

11. Garnish: Before serving, sprinkle the top with powdered sugar for a beautiful touch. You can also drizzle extra maple syrup over the casserole or top it with fresh berries or sliced bananas.
12. Serve: Cut the casserole into squares and serve warm with your favorite toppings. It’s perfect with a hot cup of coffee, tea, or freshly squeezed juice.