Heat the oven to 400°F. Lightly grease 8 cups of a standard muffin tin.
Add the ground beef, egg, breadcrumbs, onion, adobo sauce, smoked paprika, salt, black pepper, and 2 tablespoons of the barbecue sauce to a mixing bowl. Mix gently until just combined.
Divide the mixture among the 8 prepared muffin cups. Shape each portion into a loose mound, then spread the remaining barbecue sauce over the tops.
Bake for 20 to 25 minutes, until the muffins are cooked through and browned at the edges.
While the muffins bake, put the sweet potato chunks in a saucepan and cover them with water. Bring to a boil, then simmer until the potatoes are very tender, about 15 to 20 minutes. Drain well.
Mash the sweet potatoes with the butter and milk until smooth. Serve the meatloaf muffins with a scoop of sweet potato mash.