Spray the oil into a large heavy bottomed pan over a medium heat.
Chop the onion and garlic and add to the pan. Gently cook for 5 minutes until they've softened.
Meanwhile chop the root vegetables.
When the onion is soft add the chopped veggies and the tomatoes, then stir-fry them for a couple of minutes. Add the spices and stir for a minute to coat the veggies well. Stir in the tomato puree.
After a minute of stirring add the stock and bring to a boil. Put a lid on and gently cook for 15 minutes until the veggies are tender.
Chop the courgette and drain the chickpeas. Add these to the curry. Bring to the boil and let it bubble until the sauce is reduced and thickens.
Rinse the spinach, add to the curry, then put the lid on and cook for 1 more minute then turn the heat off and let it rest for a few minutes before serving.