Wash the aubergine and cut it into cubes. Place it in a colander with a teaspoon of salt and leave for 20 minutes while the moisture draws out. After 20 minutes, pat the aubergine dry with a cloth.
Cut the onion, chilli, ginger and garlic finely or add to a food processor.
For the ground cumin and coriander, you can either use powdered spices or you can toast the seeds in a dry frying pan for a few minutes until it becomes fragrant and then pound them to a rough powder with a pestle and mortar.
Heat the oil in a pan and fry all the curry spices together (apart from the garam masala, cinnamon stick and curry leaves) for a minute on a medium heat so it releases its flavour.
Add the onion, ginger, garlic and chilli paste and continue to stir.
Now add the aubergine, mushrooms, chickpeas and tomatoes along with the vegetable stock, salt/pepper, curry leaves, cardamon pods and cinnamon and simmer for 30 - 40 minutes until the chickpeas are cooked.
During the last 10 minutes of the cooking process add the garam masala and spinach and stir through.
Serve the curry with white basmati rice, fresh coriander, mango chutney, atchar and a poppadom.