Heat 2 tablespoons of olive oil and 15g of unsalted butter until foaming. Cook 1 finely chopped onion with a pinch of salt over low heat for 15 minutes, then add 1 large crushed garlic clove for 1 minute.
Stir in 350g of risotto rice for 1 minute. Add 150ml of dry white wine and reduce by half, then add half of 1.2 liters of hot vegetable stock and simmer until mostly absorbed.
Add the remaining stock a ladle at a time until the rice is tender, 20-25 minutes in all. Stir in 150g of finely grated Parmesan and the zest of 1 lemon, season, and spread on a rimmed baking sheet to cool.
Cut 150g of fresh mozzarella into 18 pieces. Divide the cooled risotto into 18 portions and shape each around a piece of mozzarella into a ball slightly larger than a golf ball.
Roll each ball in 150g of all-purpose flour, then 3 lightly beaten eggs, then 150g of fine dried breadcrumbs.
Half-fill a heavy-based pan with vegetable oil and heat over medium-low to 340°F / 170°C. Fry in batches for 8-10 minutes, until golden and the mozzarella has melted.
