Break one of the eggs into the rice and mix well. Form the rice into 2-inch balls. With your thumb, make a small indentation into the center of each ball, fill with a little mozzarella and prosciutto (if you're using it); reseal the ball with the risotto around it.
2.
Lightly beat the remaining two eggs and dip each ball into the egg mixture and then the bread crumbs. Set the finished balls on waxed paper; they can be refrigerated for up to a couple of hours or cooked right away.
3.
Put about 3 inches of oil in a deep saucepan and turn the heat to medium-high; bring to 350 degrees (at this temperature, a breadcrumb will sizzle, but not violently, when you put it in the oil). Gently slide the balls into the oil and fry until golden brown, turning once if necessary, about 4 minutes.
4.
Drain on paper towels and serve hot or at room temperature.