Ingredients :

• The potatoes — Choose waxy potatoes — like Monalisa or Charlotte. They hold up during cooking without turning into mush between the layers. Cut them into even slices of about 4-5 mm: too thick and they stay hard in the center, too thin and they disappear into the sauce.
• The ground beef — Use at least 15% fat. Beef that is too lean results in dry, flavorless meatballs. If you can, ask your butcher to grind some chuck — the difference is clear. 750 grams for 4 people is generous, and that’s intentional.
• The mozzarella — Use low-moisture shredded mozzarella for the topping, not fresh balls in water — they are too wet and will release water during cooking, making everything soggy. A pizza-style mozzarella, dry and stretchy, is what you need here.
• The paprika — A teaspoon in the meatballs might seem like little, but it’s what gives them that appetizing reddish tint and a slight sweet heat at the end. Smoked sweet paprika if you have it on hand — it’s even better.