Leave the leftover risotto to get completely cold – preferably refrigerated overnight.
Stir the tomato and Parmesan through the risotto.
Shape into equal balls, pushing a small cube of mozzarella into the centre of each one and shaping the rice around it.
If you prefer, you could make finger shapes instead.
Lay out the flour, egg and breadcrumbs on separate plates.
Dip the risotto balls into the flour, then the egg, then the breadcrumbs.
Use one hand and keep the other clean for ease.
Heat the oil to 180C or until a cube of bread sizzles when dunked in.
Fry the risotto balls until golden and crisp all over.
Serve hot or warm.