Preheat the oven to 350°F/180°C.
Add to a large mixing bowl the onion, garlic, bbq sauce, breadcrumbs, egg, Worcestershire sauce and salt and pepper. Mix with a large wooden spoon until well combined.
Press the meatloaf mixture into the base of a 9 x 13 inch baking dish. Bake for 30 minutes.
While the meatloaf is baking, Add the potatoes to a large saucepan and cover with water. Place over a medium-high heat. Bring to the boil, and cook for approximately 15 minutes, or until tender.
Drain the water from the saucepan, and add the butter, milk and sour cream. Mash the potatoes until smooth. Season to taste with salt and pepper.
Spread the mashed potato evenly over the meatloaf base. Top with the shredded cheese and bacon bits, and return to the oven to bake for a further 15 minutes, or until the cheese is bubbly and golden. Top with the fresh parsley, if using, before serving.