Preheat your oven to 350°F (175°C). Grease a baking dish with melted butter to prevent sticking.
Layer the slices of bread evenly across the bottom of the dish, creating a solid base that will soak up the custard.
Spread the sliced apples evenly over the bread, distributing the pieces so they fill all areas and begin to caramelize as they bake.
In a mixing bowl, whisk together eggs, milk, brown sugar, cinnamon, and nutmeg until the mixture is smooth and fragrant.
Pour the custard evenly over the bread and apples, pressing gently to help the bread absorb the mixture and soften.
Let the assembled casserole sit for about 10 minutes to allow the bread to soak up the custard, which helps soften the texture and develop flavor.
Place the dish in the preheated oven and bake for about 40-45 minutes, until the top is golden brown and the custard is just set with a slight jiggle in the center.
Remove from oven and let cool for a few minutes. The caramelized apples and the crispy edges provide a tempting contrast to the soft soaked bread.
Slice and serve warm, optionally drizzled with maple syrup or topped with whipped cream for extra indulgence.
