Prepare the two beef involtini, which will cook in the tomato sauce before adding the meatballs, making the sauce even tastier. Beat the eggs with the Parmigiano Reggiano and the chopped parsley, add salt and pepper and prepare an omelet.
Divide the omelet in a half, place each half onto a slice of beef. Wrap the beef slices onto themselves to form two rolls and secure the involtini with a piece of butcher’s twine. Set them aside.
Chop finely an onion and scrape it into a large thick-bottomed pot. Pour in a few tablespoons of extra virgin olive oil and season with a pinch of salt, which will help to cook the onion without letting it burn.
When the onion begins to sizzle, add the two beef involtini in the pot and brown them on each side, over medium heat.
Pour in the tomato sauce and dilute it with the warm water. Stir well and move the pan over low heat. Cover the pot and cook undisturbed for about an hour, checking from time to time that the tomato sauce is not sticking. If you see that the tomato sauce is thickening too fast, add some more water. Taste and adjust the salt.
While the tomato sauce is simmering away on the stove, prepare the meatballs.
Collect the minced meat in a bowl, then add the chopped parsley, the beaten egg, the grated Parmigiano Reggiano, then season with the salt and a few grinds of black pepper. Mix the ingredients with your hands until smooth.