Sauce
In a pan, put the onion, the garlic and sauté, add the ground beef, salt and black pepper to taste, stir-fry the meat, add some parsley and chives and the tomato sauce, add the water, mix and let it all cook .
Mash well the preboiled potatoes.
Into a pan, add the butter, salt to taste and add the mashed potatoes. Mix well and gradually add the milk until a smooth creamy mixture is formed.
Into a baking dish, add a layer of mashed potatoes and spread well, then add all the ground beef, cover with the rest of the mashed potatoes and top it all with the mozzarella cheese and some oregano to taste.
Bake in a preheated oven at 180°C (356°F) until the cheese melts and browns.
Serve.