In a skillet over medium heat, melt butter. Saute grated onions until soft, about 8 minutes. Add garlic and saute another minute. Remove from heat and allow to cool.
In a large bowl, combine the sauteed onions, ground beef, ground pork, chicken stock, eggs, Parmesan, breadcrumbs, kosher salt and black pepper. Mix well and form into a rectangle about 12 x 8 inches on a piece of parchment paper.
Top with spinach, parsley and shredded mozzarella. Roll the meatloaf up, using the parchment to keep the roll tight.
Preheat oven to 350 degrees. In a small bowl, mix the ketchup, tomato paste, apple cider vinegar, brown sugar, Worcestershire sauce, cayenne and garlic powder. Baste the top of the rolled meatloaf with the ketchup mixture.
Wrap the basted meatloaf with bacon and bake for about 1 hour and 15 minutes, until cooked through. Let rest for 15 minutes, slice and serve.