1 Heat the olive oil in a large saucepan. Add the onion and cook gently for 5 minutes. Add the rice and stir around in the hot oil for a few seconds.
2 Gradually add the stock, a little at a time, until all the liquid has evaporated and the rice is cooked, adding more stock if necessary. Leave to cool. Once cooled, season well and add the Mozzarella, tomatoes and pesto.
3 Take 60g cooled rice (about 3 tbsp), place a little nduja in the centre and mould the rice around it to form a ball.
4 Put the flour, eggs and breadcrumbs on separate plates. Dip each rice ball in the flour, egg and then breadcrumbs, coating well, and continue until all the rice has been used. You should make roughly 15 balls.
5 Place the balls on a tray and chill in the fridge for at least 1 hour.
6 Heat the oil in a deep fat fryer to 180°C. Deep fry the Arancini in batches, for approx. 5 minutes, or until golden brown and the centre is cooked. Drain on kitchen paper and serve immediately.