Butter the bottom and sides of a 13 x 9 inch baking dish.
Slice the french bread into 3/4 inch slices and lightly butter each piece on one side. Cut each slice through the middle then into bite size cubes.
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 layer, and arrange the top layer of buttered bread cubes over the cheese.
In a medium mixing bowl, whisk together 2 cups of whole milk, 1 cup of low fat half and half, 6 large eggs, 2 Tbsp Dijon mustard, 2 Tbsp maple syrup, 1 tsp salt, 1/2 tsp onion powder and 1/4 tsp black pepper. Add 1-2 tablespoons of chopped chives.
Pour the custard evenly over the layers of bread cubes, ham and cheese.
Using a spoon, gently press the bread cubes into the custard, then cover tightly with plastic wrap.
Place the dish into the refrigerator to chill overnight to allow the bread to soak in all of the luscious custard.
To 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.
Bake for 45-50 minutes or until the top is golden and the egg custard has set and cooked through.
Allow the casserole to sit on the counter for 5 minutes before cutting into squares and serving. Serve drizzled with pure maple syrup.