Meatballs Baked with Potatoes, Cheese and Creamy Bechamel

Ingredients

• 3 large russet potatoes, about 1 1/2 lb (680 g), peeled and sliced 1/4 inch thick
• 1 tablespoon salt, for the potato water
• 1 tablespoon olive oil, for greasing the dish
• 1 1/2 lb (680 g) ground beef, 80 to 85 percent lean
• 1 small yellow onion, finely grated or minced
• 2 cloves garlic, minced
• 1 large egg
• 1/2 cup (45 g) plain breadcrumbs
• 2 tablespoons chopped parsley
• 1 teaspoon sweet paprika
• 1 teaspoon kosher salt
• 1/2 teaspoon black pepper
• 4 tablespoons (56 g) unsalted butter
• 1/4 cup (32 g) all-purpose flour
• 3 cups (720 ml) warm whole milk
• 1/2 teaspoon kosher salt
• 1/4 teaspoon black pepper
• 1/8 teaspoon ground nutmeg
• 2 cups (225 g) shredded low-moisture mozzarella
• 1 tablespoon chopped parsley, for serving