In a mixing bowl, mix the rice, chopped chorizo, Parmesan, eggs and, optionally, salt and pepper.
Scoop some of the rice mixture using a measuring spoon or small ice cream scoop. Place a cheese cube at the center. Gather to form a ball making sure that no part of the cheese is exposed. Repeat until all the rice mixture has been used.
Place the rice balls in container in a single layer. Cover the container and chill the rice balls for at least 30 minutes.
Start heating the oil in a wok or frying pan.
Take the rice balls out of the fridge and roll each one in panko.
When the oil has reached a temperature of 350F, fry the rice balls in batches. Turn then around occasionally for even frying. When the crust is a golden brown, scoop out and move to a plate lined with paper towels.
Serve the arancini-style cheese-stuffed rice balls with tomato sauce on the side for dipping.