Line a 6-quart slow-cooker or a larger slow-cooker using a huge sheet of aluminum-foil. Grease with cooking spray and put aside.
In a large mixing-bowl combine ground-beef, breadcrumbs, garlic, onions, Italian-Seasoning, salt, pepper, ground-mustard, egg, milk & Worcestershire-sauce. Mix together with your hands until blended, but don't overmix.
Split meat in half.
Press one half the meat to the base of the toaster.
Spread shredded mozzarella down the middle, leaving approximately ½ inch space around the sides.
Top with remaining meat & form it into a loaf, and press around to seal the borders. Put aside.
In a small mixing bowl whisk together the barbecue-sauce, honey, ketchup, Worcestershire-sauce, along with Sriracha-sauce.
Brush half the glaze over the meatloaf. Reserve the remaining half to later.
Cover and cook on LOW for 6hours on HIGH for 3-4hours. Meatloaf is completed when temperature reaches 160˚F within an Instant Read Thermometer.
Lift the meatloaf by holding on the foil, move to a baking dish & top with the remainder of the glaze.
Pop it under the broiler for 3-4 mins, or until browned.
Remove from oven and let rest for 10 mins. Then garnish with parsley and serve.