Put the canned tomatoes, sun-dried tomatoes, tahini, half of the chickpeas and harissa, if using, into a blender. Blitz until smooth.
Pour the mixture into a pot, then add one full can of water, the rest of your chickpeas, and the stock cube. Simmer for 5-10 mins until the chickpeas have softened slightly and the tomatoes have cooked, mashing down some of the chickpeas with a fork if you like, to create a chunky texture. Taste and season well with salt and pepper.
To serve, ladle the soup into bowls and drizzle with tahini, olive oil and harissa. Sprinkle over some sesame seeds, if you like.
