Spray the bottom and sides of a 13x9-inch baking dish with nonstick cooking spray. Set aside.
Slice the french bread into 3/4-inch thick slices and lightly butter each piece on one side using 2 Tbsp of softened butter. Cut each slice into bite size cubes. (About 1/2-3/4 inch)
Layer half of the buttered bread cubes in the bottom of the baking dish. Arrange the cubed ham over the bread.
Sprinkle 1 cup of shredded Swiss cheese over the cubed ham. Top with reserved bread cubes.
In a medium mixing bowl whisk together whole milk, half and half, large eggs, Dijon mustard, maple syrup, salt, garlic powder, onion powder and black pepper. Add 1-2 tablespoons of chopped chives. Stir to combine.
Pour the egg mixture evenly over the layers of bread, ham and cheese.
Using the back of a spoon, gently press the bread cubes into the egg custard, then cover tightly with plastic wrap.
Place the dish into the refrigerator to chill for 8 hours or overnight to allow the bread to soak in all of the luscious custard.
Bake: Allow 15-20 minutes on the counter. Preheat the oven to 375°F.
Remove plastic wrap. Sprinkle the remaining shredded Swiss cheese on top and dot the top with small, thin pats of butter. (There's 2 Tbsp left, but you can use more to your taste).
Bake for 45-50 minutes or until the top is golden brown and the center is set when the dish is gently shaken. The egg custard should be set and cooked through.
Allow the casserole to stand on the counter for 5 minutes before cutting into squares and serving drizzled with pure maple syrup.