Grease a 9x13 casserole dish. Layer the dried bread in the bottom of the dish.
In a large bowl, whisk together the eggs, milk, half & half, sugar, vanilla, cinnamon and nutmeg. Mix well. Pour over the bread.
Pat plastic wrap over the bread and refrigerate for at least 8 hours. Place a couple of small appetizer plates on top of the plastic wrap to keep the bread submerged, if necessary.
Preheat oven to 350. Place a piece of foil on the rack to catch any potential dripping. Remove the french toast from the refrigerator.
In a medium bowl, combine the butter, maple syrup, brown sugar and chopped pecans. Mix until crumbly.
Spoon the topping evenly over the French toast. Bake at 350 for about 1 hour or until puffed and golden. Cool for 10 minutes before serving. Serve with additional maple syrup, optional.