Heat the oil in a large skillet over medium heat and sauté the onion, celery, and carrots until the onion turns translucent and begins to brown, about 5 to 10 minutes. Add the turmeric, cumin, harissa or chile flakes, 1 teaspoon of salt, 1 cup each of the parsley and cilantro, tomatoes, and the stock. Bring to a boil. If using soaked chickpeas, drain and add to the pot. Simmer uncovered for 25 minutes, then add lentils, another teaspoon of salt, and a teaspoon of pepper. Continue simmering until the chickpeas and lentils are cooked, about 20 minutes more. If using canned chickpeas, omit the first 25 minutes of simmering and add with the lentils.

Whisk the flour, egg, and lemon juice into 2 cups (470 ml) of water. Stir into the soup. Simmer around 5 more minutes and serve, sprinkled with the remaining cilantro and parsley. Serve with extra harissa on the side.