Heat the oil in a soup pot. Add the onion and garlic and sauté over medium-low heat until golden.
Add the water with bouillon cubes, mushrooms, cabbage, and seasonings. Bring to a rapid simmer, then lower the heat. Cover and simmer gently for 15 minutes.
Meanwhile, set aside half of the chickpeas and place the remainder in a food processor or blender with the tahini. Add a little water as needed to thin the consistency. Process until smoothly pureed. Stir the puree back into the soup pot.
Stir in the reserved chickpeas, bring to a simmer, then cover and simmer very gently for 10 minutes.
Stir in the parsley, scallions, dill, and lemon juice. Add water as needed for a medium-thick consistency.
Season with salt and pepper, then simmer for 5 minutes longer. Serve at once, or let stand off the heat for an hour or two. Heat through before serving.