Vegetable curry for a crowd

INGREDIENTS

• 1 large potato , diced
• 1 small butternut squash , peeled, deseeded and diced
• 1 aubergine , diced
• 6 tbsp tikka masala paste
• 3 tbsp vegetable oil
• 2 onions , sliced
• 680g-700g jar tomato passata
• 400g can coconut milk
• 2 red peppers , sliced
• 2 courgettes , diced
• few coriander sprigs, to serve
• rice or naan bread , to serve