Combine mince, half the basil, half the garlic and 1 cup breadcrumbs in a bowl. Season with salt and pepper. Using 1 heaped tablespoon at a time, roll mixture into balls. Place on a baking tray. Using your thumb, make a large indent in the middle of 1 meatball. Place one cube of cheese in hole. Re-roll mince mixture to enclose cheese. Repeat with remaining meatballs and cheese.
Place flour and remaining breadcrumbs in separate shallow bowls. Lightly whisk eggs in another shallow bowl. Coat balls in flour, shaking off excess. Dip in egg, then coat in breadcrumbs. Return to tray.
One-third fill a large saucepan with vegetable oil. Heat over medium heat. Cook balls in batches, turning often, for 4 to 5 minutes or until golden and cooked through. Transfer to paper towel to drain.
Meanwhile, heat extra virgin olive oil in a saucepan over medium-high heat. Add remaining garlic. Cook, stirring for 30 seconds or until fragrant. Add passata. Stir in vinegar and sugar. Bring to the boil. Reduce heat to low. Simmer, stirring occasionally, for 15 minutes or until thickened. Stir in remaining basil. Transfer to a serving bowl.