Heat the olive oil over medium heat in a skillet. Add the onion and cook for 5 minutes. Add the garlic, cook 2 minutes more and set aside to cool.
In a large mixing bowl, thoroughly combine the ketchup, 1/4 cup bbq sauce, egg, breadcrumbs, parsley, salt, pepper and the cooled onion mixture. Add the turkey and beef sirloin and mix until just combined.
Pack the mixture into a 9-inch loaf pan, brush the top with the remaining bbq sauce and bake covered for 1 hour. Let stand 10 minutes before slicing.
Slice off top of garlic bulb and drizzle with olive oil. Place in aluminum foil or ovenproof dish in same preheated oven as the meatloaf for 15-20 minutes. Remove from oven and let cool.
Boil the potatoes in a large pot of water until done, about 10-15 minutes depending on the size of the potatoes.
In a small saucepan, bring the stock to a boil and turn down to a simmer.
Squeeze the roasted garlic cloves into a small bowl to release each clove of garlic. Throw the skins away and mash garlic with a fork.
Drain the potatoes and mash (with their skins on). Add the roasted garlic. Slowly add the stock until the desired consistency is reached.