Baked pasta with tomatoes & mozzarella (Pasta al forno con pomodori e mozzarella)

INGREDIENTS

• sea salt
• freshly ground black pepper
• extra virgin olive oil
• 1 white onion, peeled and finely chopped
• 2 cloves garlic, peeled and finely sliced
• 1-2 dried red chillies, crumbled
• 1.5 kg ripe tomatoes, or 3 x 400g cans of good-quality plum tomatoes
• 1 large handful fresh basil leaves
• 1 tablespoon red wine vinegar, optional
• 14 oz dried orecchiette
• 4 big handfuls Parmesan cheese, freshly grated
• 3 x 5 oz mozzarella balls