Place the oil in a large pot set over medium heat. Add the leek, onion, carrot, bell pepper and garlic and cook 5 minutes. Mix in the diced tomatoes, tomato sauce, orange zest and juice, honey, spices, oregano and chickpeas. Bring to a simmer, and simmer the stew, partially covered, for 15 minutes, or until the vegetables are tender. Mix in the tuna and olives and cook a few minutes more, until heated through. Taste the stew, and season with salt and pepper, if needed. Sprinkle servings with parsley.
Recipe Options: For a more distinct herb taste, instead of parsley, sprinkle the stew with chopped fresh basil, mint, or oregano. Instead of canned tuna, grill, cool, cube and add a 200-gram piece of albacore tuna to the stew. If you don't care for tuna, simply make the stew without it.