Preheat oven to 350 degrees F. Lightly grease a 1 quart baking dish. Bring a large pot of salted water to a boil and add sweet potato. Cook until tender, about 8 to 10 minutes. Drain and blend until smooth.
In a large bowl combine ground turkey, yolk, onion, garlic, barbeque sauce, ketchup, mustard, both bread crumbs, pepper and salt. Mix very well until evenly distributed.
Place into baking dish and using your hands mold into a loaf. Bake in preheated oven for about 1 hour and 10 minutes, until golden and cooked through.