Mix chilled rice, eggs, and peas together.
Roll into balls about the size of a tangerine and place one cube of cheese into the rice ball; reform balls firmly to hold shape.
Place flour, egg and breadcrumbs into 3 separate bowls.
Dip each ball in flour, shaking off excess and reform if needed.
Dip in egg, letting excess drip off, then dredge in breadcrumbs, reforming and transfer to a sheet of wax paper.
Repeat with remaining balls.
Meanwhile heat 2 inches of oil in a 4- to 5-quart heavy pot until thermometer registers 350-360 degrees.
Working in batches of 4-6 balls, lower rice balls into oil with a slotted spoon and fry, turning occasionally, until golden brown, 2 to 3 minutes per batch.
Transfer with slotted spoon to paper towels to drain.
Return oil to 350-360 degrees between batches.
Serve with a tomato sauce.
Ready in 40 min 20 min prep.