Preheat the oven to gas mark 6, 200C, fan 180°C In a large roasting tin, toss the meatballs in 1tbsp oil, until coated. Bake for 10 minutes, then remove from the oven, toss the meatballs and pour in the passata. Return to the oven for 10 minutes.
Remove the tray from the oven and scatter over the mozzarella. Top with the ciabatta slices, pressing them into the sauce slightly.
Drizzle the bread with the remaining 1tbsp oil and return to the oven for 10 minutes, or until the bread is crisp, the cheese is melted, and the sauce is bubbling. Scatter over the basil and serve with a mixed salad, if you like.