Preheat your oven to 375°F (190°C).
Grease a 9x13-inch baking dish.
Cut the challah bread into 1-inch cubes.
In a large bowl, whisk together the eggs, milk, Dijon mustard, vanilla extract, and seasonings.
Layer half of the bread cubes in the greased baking dish.
Sprinkle half of the diced ham and shredded cheese over the bread.
Pour half of the egg mixture over the first layer.
Repeat the layers with the remaining bread, ham, cheese, and egg mixture.
Drizzle maple syrup over the top of the casserole.
Bake for 45-50 minutes, until the top is golden and the custard is set.
Let the casserole rest for 10-15 minutes before serving.
