Preheat oven to 350°F and grease a loaf pan with butter or nonstick spray. Set aside.
To a medium bowl, add the chicken, egg, onion, garlic, Dijon, parmesan, parsley, salt and pepper, and 1/4 cup of the breadcrumbs. Using your hands, mix until evenly combined.
Place mixture onto a rectangular piece of parchment or wax paper and flatten into a rectangle that’s about 8 by 12-inches.
Line meat mixture with ham slices, followed by Swiss cheese slices.
Using the parchment paper, roll the meat mixture up into a log, starting at a short end.
Use paper to transfer meatloaf to prepared pan and place seam side down. (Remove the paper.)
Mix together the remaining breadcrumbs and the melted butter (and a pinch of salt) and sprinkle over meatloaf.
Bake until a meat thermometer reaches 165°F, about 75 minutes. (Start checking at 1 hour.)
Remove meatloaf from oven and let rest while you make the sauce:
In a saucepan over medium heat, melt the butter. Whisk in flour and cook 1 minute, whisking constantly.
Gradually whisk in milk and cook until starting to thicken, about 3 minutes.
Whisk in mustard and cheese until melted. Season to taste with salt and pepper. Serve over meatloaf. Enjoy!
