Dice the onion and mince the garlic. Cook both in a large pot with olive oil over medium heat until soft and translucent. Add the coriander stems and ginger and spices and cook until you can smell the aroma of spices, but not burnt. Add the tomatoes and continue to stir and cook for a further 5 minutes.
While the ingredients in the first step are cooking, peel and dice the potato and carrots. Rinse the lentils. Once the tomato has reduced to a thick sauce, add the carrots, potato, and lentils to the pot.
Add 6 cups of vegetable broth. Give everything a good stir to make sure it’s mixed well. Place a lid on top, turn the heat up to high, and bring the soup to boil. As soon as it reaches comes to the boil, turn the heat down to its lowest level and allow it to simmer for 30 minutes.
After it has simmered for 30 minutes give the pot a stir and add the salt, starting with ½ teaspoon. Add more if desired. I used about ¾ teaspoon total. Stir through the Spinach at the end so it just melts into the stew, and garnish with Coriander leaves. Serve hot!