1. To make the French toast, grease a 9" x 13" baking dish with the butter. Arrange the bread slices in the baking dish in two overlapping rows.
2. Whisk together the eggs, eggnog, milk, sugar, vanilla, cinnamon, nutmeg, and salt in a large bowl. Pour the egg mixture evenly over the bread slices, making sure the bread is well covered. Cover and refrigerate overnight.
3. Preheat the oven to 350°F. Remove the baking dish from the refrigerator.
4. To make the topping, whisk together the butter, brown sugar, pecans, corn syrup, cinnamon, and nutmeg in a medium bowl until thoroughly combined. Sprinkle the topping evenly over the bread.
5. Bake for 30-40 minutes, until lightly browned. Remove the casserole from the oven and decorate with the maraschino cherries in clusters of three to look like holly berries. Serve with maple syrup.
Cook's Note: It's best to use day-old bread , so the custard can really absorb. The casserole can be made the night before and refrigerated. Perfect for Christmas morning