Preheat oven to 160c/gas3. Heat oil in large flameproof casserole. Add onion and gently cook until softened - approx 5 minutes.
Stir in garlic, ginger and spices & fry gently for 2 minutes. Add the tomatoes, aubergine and courgette.
Next add the stock, tomato puree, potato and chickpeas. Bring to the boil, cover and cook for 1 hour in the oven.
Blend the yogurt with half of the spring onions.Add the coriander and mint.
Remove casserole from the oven. Take 3tbsp of vegetables from the casserole, mash them up and return them to the casserole (this will thicken the sauce).Stir in the spinache and return to the oven for a further 10 mins cooking time.
Serve topped with a spoonful of yogurt and chopped spring onions.