Supplì (Roman Rice Croquettes)

Name: Supplì (Roman Rice Croquettes)
Prep time: 30 min
Cook time: 50 min
Total time: 50 min
Yield: 6 pieces
Ingredients: 80 g onions; 30 g extra virgin olive oil; 1 garlic clove; 400 g tinned chopped tomatoes; ½ Tbsp balsamic vinegar; 3 fresh basil leaves; 1 tsp caster sugar; ½ tsp fine sea salt; 1 pinch ground black pepper; 100 g bread; ¼ tsp fine sea salt; 1 pinch ground black pepper; 600 g risotto rice; 100 g fresh mozzarella; 2 medium eggs; vegetable oil