Preheat the oven to 400°F and grease a round glass baking dish.
Parboil the potato slices in salted boiling water for about 15 minutes. Drain and set aside.
In a mixing bowl, combine ground beef, diced onion, minced parsley, paprika, salt, and black pepper. Form the mixture into 15 evenly-sized meatballs.
In a saucepan, melt butter and stir in flour. Cook until the mixture bubbles, then gradually add heated milk, stirring constantly until thickened. Season with salt and pepper.
Arrange the potato slices in the bottom and around the sides of the prepared baking dish.
Place a meatball on top of each potato slice, filling the gaps with additional potato slices.
Pour béchamel sauce over each meatball, filling the pockets around it.
Sprinkle shredded mozzarella cheese over each meatball, filling the pockets around it.
Bake in the preheated oven for 15 minutes, or until the cheese is golden and bubbly.
Serve hot and enjoy immediately.