Preheat the oven to 200C/180C Fan/Gas 6.
To make the curry, put the potato, squash and aubergine into a large roasting tin and coat with 2 tablespoons of the masala paste and 2 tablespoons of the oil. Season with salt and pepper and roast for 30 minutes.
Heat the remaining oil in a large saucepan over a medium heat and fry the onions for 10 minutes, until soft and golden brown. Stir in remaining masala paste and cook for a further 3 minutes. Add the tomatoes, coconut milk and 100ml/3½fl oz water. Bring to the boil and simmer for 10 minutes.
Add the roasted vegetables to the pan, along with the peppers and courgettes and simmer for 10–15 minutes, until tender.
To make the naan, preheat the oven to 230C/210C Fan/Gas 8.
Place the flour, baking powder, salt, milk and oil in a large bowl and mix to form a smooth dough. Allow to rest for 1 hour.
Roll out the dough into naan shapes and top with the tomatoes and garlic. Bake for 10 minutes until puffed up. You can finish the naan under a hot grill if you wish.
Scatter the curry with coriander and serve with the naan breads on the side.