Step 1: Prepare the Baking Dish
Start by generously buttering a 9×13-inch baking dish. This ensures that the French toast won’t stick and will have a nice buttery flavor. Arrange the bread slices in a snug, single layer, overlapping them slightly if needed to fit them all in.

Step 2: Make the Custard Mixture
In a large mixing bowl, crack the 5 large eggs and whisk them until they are well beaten. Add 1 cup of half-and-half, 1 cup of whole milk, 1 teaspoon of vanilla extract, 2/3 cup of granulated sugar, 1/4 teaspoon of ground cinnamon, and 1/4 teaspoon of ground nutmeg. Whisk everything together until the mixture is smooth and the sugar is well incorporated. This mixture will soak into the bread, creating a rich, custardy texture.

Step 3: Soak the Bread
Evenly pour the custard mixture over the arranged bread slices. Make sure every piece of bread is thoroughly soaked in the mixture. This step is crucial for achieving the right texture, as the bread needs to absorb the liquid to become soft and custardy.

Step 4: Refrigerate Overnight
Cover the baking dish with plastic wrap and refrigerate overnight. This overnight soak allows the bread to fully absorb the custard mixture, resulting in a deeply flavorful and creamy French toast.

Step 5: Preheat the Oven
In the morning, preheat your oven to 350°F (175°C). Remove the baking dish from the refrigerator and take off the plastic wrap.

Step 6: Add Butter and Sugar
Cut 1/4 cup of unsalted butter into small pieces and scatter them evenly across the top of the soaked bread. Sprinkle a bit more granulated sugar over the top. This will add a touch of sweetness and help create a caramelized crust as the French toast bakes.

Step 7: Bake the French Toast
Place the baking dish in the preheated oven and bake for 35-40 minutes, or until the bread is puffed and golden. The French toast should resemble a crisp autumn day with its golden brown top and puffed appearance.

Step 8: Caramelize the Sugar
Once the French toast is baked, let it cool briefly. For the final touch, sprinkle a bit more granulated sugar on top of the French toast. Turn on your oven’s broiler and place the baking dish under it for a few minutes, or until the sugar caramelizes into a crackling, golden crust. Keep a close eye on it to prevent burning.