1. Spray a 9 x 13-inch baking pan with cooking spray. Tear French bread into chunks, or cut into cubes, and evenly place in the pan.
2. In a large bowl, mix together eggs, eggnog, sugar, vanilla extract, and nutmeg. Pour evenly over bread. Cover pan with saran wrap and store in the refrigerator for several hours or overnight.
3. In a separate bowl, mix together flour, brown sugar, cinnamon, nutmeg, and salt. Add butter pieces and cut into the dry mixture using a fork or your hands. Combine until the mixture resembles sand with a few pea sized chunks. Cover and store mixture in the refrigerator.
4. When you’re ready to bake the French toast, preheat oven to 350 degrees F. Remove French toast from refrigerator and sprinkle crumb mixture over the top. Bake for 45-55 minutes, or until the French toast is set and golden brown.
5. Serve warm with maple syrup, if desired.