Gobi aloo (cauliflower and potato curry)

Ingredients

• 1 teaspoon olive or rapeseed oil
• 1 onion, finely chopped
• 2 cloves garlic, crushed
• 1 x 200g can chopped tomatoes
• Pinch ground turmeric
• 1 teaspoon ground coriander
• 1 teaspoon ground cumin
• 1 teaspoon garam masala
• 1 or 2 green chillies, deseeded and chopped (optional)
• 200g new potatoes, scrubbed and cut into bite-sized pieces
• 100–150ml hot water
• 1 small cauliflower, cut into florets
• Handful of fresh coriander leaves and stems, chopped