1. Combine first 3 ingredients in a large bowl; mix well. Press 2 tablespoons rice mixture around 1 cube of cheese to form a small ball. Repeat with remaining risotto and cheese.
2. Place flour in a shallow bowl; place breadcrumbs in a second shallow bowl. Beat egg with 2 tablespoons water in a third bowl. Dredge rice balls in flour, dip in egg mixture, and roll in breadcrumbs to coat. Place on a tray, cover loosely with plastic wrap, and chill at least 30 minutes or up to 24 hours.
3. Pour oil to a depth of 3 inches in a deep saucepan; heat to 350°. Fry rice balls, in batches, 4 to 5 minutes or until golden. Remove with a slotted spoon; drain on paper towels. Serve warm.