Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the ground beef, breadcrumbs, egg, milk, chopped onion, minced garlic, Worcestershire sauce, barbecue sauce, salt, pepper, and smoked paprika. Mix until well combined.
Transfer the meat mixture into a greased baking dish (9x13 inches), shaping it into a loaf shape.
In a large skillet, bring water to a boil and add the sliced potatoes. Cook for about 10-15 minutes, until slightly tender. Drain the potatoes.
In a bowl, mix the drained potatoes with shredded cheddar cheese, sour cream, melted butter, garlic powder, and salt until well combined.
Spread the potato mixture evenly over the meatloaf in the baking dish.
Bake in the preheated oven for 1 hour, or until the meatloaf is cooked through and the potatoes are golden brown.
Let the casserole rest for 10 minutes before slicing and serving.