If you'd rather not bother with stuffing the meatballs, roast large meatballs and simply serve with dollops of fresh ricotta cheese alongside or atop the meatballs.
Wrap a 1-inch cube of Fontina, mozzarella or provolone cheese or a halved hard-boiled egg with half a slice of prosciutto each. (Cheese and/or egg may also be wrapped in spinach leaves or a combination of spinach and ham.) Form large 4-inch meatballs around each piece of cheese or egg.
Arrange balls on cooling rack set over a baking sheet and drizzle with oil. Roast until brown and crispy all over in a 400F oven, 25-30 minutes. Serve 2 balls per person in shallow bowls sitting in a pool of tomato sauce, passing crusty bread at the table for mopping.