Melt butter in a large saucepan and saut the onion and garlic for 5 minutes. Add the rice and stir until well coated, then add 1 cup of stock at a time until it’s absorbed and rice is cooked. Stir in parmesan and seasonings, then leave to cool.
Place flour in a shallow bowl, egg and milk combined in another and breadcrumbs in a third shallow bowl.
Make a ball with one tablespoon of risotto, roll in the flour, egg mixture and then coat in breadcrumbs. Repeat with the remaining mixture to make 24 balls.
Heat oil in a frying pan, add the arancini balls and fry until golden brown.
Transfer to a plate lined with paper towel and place on a serving plate to serve.