In a small bowl, combine panko and milk. Let sit 5 minutes until the breadcrumbs absorb the liquid - this keeps the meatloaf tender and prevents a dry, crumbly texture.

Whisk together Dijon mustard, ketchup, and brown sugar in a small bowl. Set aside half for serving, reserve the rest for topping the meatloaf.

In a large bowl, combine ground beef, ground pork, soaked panko mixture, egg, onion, garlic, thyme, 1 teaspoon salt, and pepper. Use your hands to mix just until combined - overworking makes the meatloaf tough.

Press half the meat mixture into the bottom of a 9x5 inch loaf pan, creating a slight well in the center. Layer ham slices over the meat, then top with Swiss cheese, leaving a 1/2-inch border. Press remaining meat mixture over the top, sealing the edges completely so the cheese stays inside during baking.

Bake at 350°F for 45 minutes. Remove from oven and spread half the glaze over the top. Return to oven and bake 15-20 minutes more, until the internal temperature reaches 160°F and the glaze is caramelized. Let rest 10 minutes before slicing - this allows the cheese to set so it doesn't run out.

Slice thickly and serve with reserved glaze on the side. The cheese center should be melted and oozy, the ham slightly crisp at the edges.