In a large pan, add the olive oil and onions and cook over medium heat for 7-8 minutes, until soft and brown.
Add in the garlic, celery and carrot. Stir to combine and cook for 2-3 minutes, stirring occasionally. Add the spices and stir until the veg is coated.
Now add the chopped tomatoes and allow them to soften a little.
Next, add the stock, lentils and harissa. Simmer for 10 minutes covered, then remove the lid and simmer for a further 10 minutes. Add the chickpeas and coriander, stir to combine.
Remove 2 cups of the soup and blend it in a food processor.
Return to the pot and serve in a warm bowl. Garnish with a little natural yoghurt and coriander.
Season well with salt and pepper.
If you find the soup too thick, add a little more vegetable stock