Grease a large rectangular baking pan (I use a lasagna casserole dish that's slightly larger than 9-inch by 13-inch) with butter.
Arrange the slices of French bread in the baking dish so the tops are facing up.
In a large bowl whisk together the eggs, milk, brown sugar, cinnamon, and nutmeg, and pour the egg mixture carefully over the bread in the casserole dish, making sure to moisten each piece completely.
Add the chopped apples to the top, along with the pecans, pushing them down slightly into the cracks between the pieces of bread.
Combine the white sugar and cinnamon in a small bowl and sprinkle it over the casserole.
Bake immediately at 350 degrees Fahrenheit for about 40 minutes, or cover with plastic wrap and place in the fridge to chill overnight.
If you choose the overnight method, simply remove the plastic wrap and add the dish to a cold oven. Preheat the oven as normal and when it reaches 350 degrees, set your timer for 40 minutes and bake as normal. The casserole dish will preheat slowly with the oven and this will prevent the dish from cracking. Never place a cold casserole dish in a hot oven!!
Remove the casserole from the oven and let cool for about 10 minutes before serving. Dust with powdered sugar and garnish with whipped cream and maple syrup when serving.
Feel free to use whatever bread you like for this recipe - any normal bread works well, as well as sweet breads like Brioche.