Start by buttering a 9x13-inch baking dish generously. Arrange slices of slightly stale French bread in a single layer, ensuring they fit snugly without overlapping.

In a large mixing bowl, whisk together eggs, half-and-half, whole milk, vanilla extract, granulated sugar, ground cinnamon, and optional nutmeg until the mixture is smooth and well-combined.

Carefully pour the prepared custard mixture over the arranged slices of French bread ensuring each piece is well-coated. Gently press down on the bread to help it absorb the custard.

Cover the baking dish tightly with plastic wrap and refrigerate overnight.

Preheat your oven to 350°F (175°C). Remove the plastic wrap and dot the top with pieces of unsalted butter. Sprinkle granulated sugar over the soaked bread.

Bake for 35-40 minutes until puffed, golden, and slightly crisped on top.

Once baked, sprinkle more sugar over the top. Use a kitchen torch or broiler until the sugar melts and caramelizes.

Allow to cool slightly before slicing into squares. Drizzle with warm maple syrup or serve with fresh berries.