Melt butter and pour in bottom of a 9x13 baking dish. In a small bowl, mix together brown sugar, cinnamon, nutmeg.
In a larger bowl, whisk together vanilla, eggs, and milk. Slice french loaf and place one layer of bread slices on bottom of baking dish. I regularly find day old french bread on clearance at Walmart for around $1.
Sprinkle with 1/2 of brown sugar mixture. Place 2nd layer of bread slices on top. Pour egg mixture even over top layer of bread slices. Sprinkle remaining brown sugar mixture over top.
Cover with foil and refrigerate until morning. To bake, cover with new foil and place in oven at 350 for 30 minutes. Remove foil and bake an additional 10 minutes. Drizzle maple syrup over top and put back in oven for about 5 minutes. Let casserole sit for about 10 minutes before serving.