Cauliflower and potato curry

Ingredients

• 3 tablespoons ghee or olive oil*
• 1 onion, finely chopped
• 4 cloves garlic, finely chopped
• 2 teaspoons finely grated ginger
• 1 tablespoon garam masala*
• pinch dried chilli flakes
• 1 teaspoon fine sea salt
• 2 medium tomatoes, finely chopped
• 3 medium (500g) potatoes, peeled and cut into 2cm pieces
• 400 millilitres cold water
• 1 medium (800g) cauliflower, cut into bite-sized pieces
• coriander leaves, to serve