In a large stockpot, pour the olive oil into the pot. Sweat the onions, celery, carrots and garlic for 10 minutes on medium heat with lid on. Stir occasionally and add in a half-cup of the vegetable stock to help the sweating/cooking process.
Add the tomato sauce, the remaining vegetable broth, Italian seasoning, and pearled couscous. Bring to a boil then reduce to medium-low. Cook for 15 minutes. Then add in the diced plum tomato, greens, and drained and rinsed garbanzo beans. Cook for an additional 5 minutes. One greens have wilted and the soup has simmered ladle soup in to bowls and top with parmesan cheese if desired.