Chop onion into small pieces. Chop garlic finely.
In a deep frying pan, fry the onion in vegetable oil until translucent.
Add lemon zest as well as minced garlic to the onion in the pan and stir fry it for about 1 minute.
Add rice, white wine and water, stir, bring to a boil and simmer with the lid on for about 20 minutes (or according to package directions from the rice) until the rice is cooked and has completely absorbed the liquid. (Note my tips and tricks for this here at the top of the post).
Cut mozzarella into small cubes and chop parsley.
Add grated cheese, diced mozzarella, and chopped parsley to the rice in the pan, stir until the cheese is melted, and remove the pan from the heat. Let the rice mixture cool, seasoning it with salt and pepper to taste.
Whisk egg in a small bowl. Finely crumble rusks in another small bowl.
Form 6 balls from the rice mixture, dip each ball in the egg and then roll in the rusk.
Spread the rice balls on a baking tray lined with baking paper and bake them in a preheated oven at 180 °C for about 10 minutes.