Preheat oven to 400°F. Mix chicken with egg, mayonnaise, ¼ cup breadcrumbs, onion, garlic powder, parsley, salt, and pepper.In a loaf pan, layer half the chicken mixture, followed by chicken ham and cheese. Repeat with remaining chicken mixture.Bake for 25 minutes, add panko breadcrumbs, bake for another 15 minutes.For gravy, melt butter, whisk in flour, add cream, milk, Worcestershire sauce, and Dijon mustard. Simmer, add Parmesan, nutmeg, salt, and pepper.Rest meatloaf, slice, and serve with gravy.