Heat 2 tablespoons of oil in a large frying pan over medium-high heat. Add the rice and stir for 2 minutes to toast. Begin adding the stock a ladleful at a time, cooking and stirring until it has all been absorbed and the rice is tender. The cooking method is similar to making risotto. It will take 15-20 minutes for the rice to be cooked. Remove from the heat and set aside to cool for 1 hour.
Heat the remaining 2 tablespoons of oil in a medium frying pan over medium heat. Add the onion and saute until softened, 3-4 minutes.
Add the chicken livers, veal, peas, and wine and simmer until the wine has evaporated about 5 minutes. Add the tomato and season with salt and pepper. Continue cooking, stirring often, until the sauce is thick and well cooked, about 20 minutes.
Combine the cooled rice, Parmesan, and butter in a bowl. Mix well and mold into round croquettes about the size of golf balls. Hollow out the center of each croquette and fill with meat sauce and a piece of hard-boiled egg. Close the rice around the filling.
Beat the raw eggs with a fork in a shallow dish. Dip the croquettes into the egg and then roll in bread crumbs.
Heat the frying oil in a deep-fryer or deep saucepan until very hot. Test the oil temperature by dropping in a small piece of bread. If it immediately bubbles to the surface and begins to turn golden, the oil is ready.
Fry the croquettes in batches until crisp and golden brown, about 5 minutes each batch. Scoop out with a slotted spoon and drain on paper towels. Serve hot.