Speedy tomato, chicken and olive pasta

Ingredients

• 500g penne pasta
• 2 tbs extra virgin olive oil
• 500g chicken breast fillets, thinly sliced
• 1 brown onion, finely chopped
• 3 garlic cloves, crushed
• 1/4 bunch continental parsley, stems and leaves separated, stems finely chopped
• 700g passata
• 1/4 cup whole kalamata olives, drained, deseeded, halved