Peel and dice the onions, thinly slice the shiitake mushrooms, removing stalks, then cut celery, carrot, capsicum/bell pepper and potatoes into small cubes.
Heat 3 tablespoons olive oil in a stock pot (at least 6 litre/quart capacity), then add onions, prepared vegetables and sliced garlic. Cook, stirring frequently for a couple of minutes or more to soften.
Add vegetable stock to the pot to loosen, then add all spices, stir well.
Rinse and drain lentils and add to the pot along with tomato paste, stir well.
Cover the stock pot with a lid, slightly ajar. Bring to a boil (approx. 5 mins), then reduce to a simmer, and cook for 20 minutes, stirring every so often to prevent burning.
Remove the lid and add washed spinach, cook a further minute or so to wilt.
If the consistency of the soup looks to your liking – squeeze over the juice of one lemon and add a sprinkle of freshly chopped coriander. If the soup is looking a little on the thicker side, add a further half cup or more of water and let simmer a further minute or two to thin it down. Enjoy!