In a heavy bottomed pot or Dutch oven, heat olive oil over medium-high heat until shimmering.
Add onions and celery. (If you want to add spice, add Calabrian chili paste now.) Sauté for 3-5 minutes, until onions are translucent. Add in carrots and garlic and sauté for an additional minute, until very fragrant.
Add in vegetable broth, chickpeas, orzo, dried oregano, and bay leaf. Occasionally stir as you bring this mixture up to a boil.
Reduce heat to low and allow the soup to simmer for 7-10 minutes, or until orzo is just slightly undercooked (a little less cooked than al dente). Then stir in your greens and allow to simmer for another 1-3 minutes, until wilted. (Spinach will require less time than heartier green like kale.)
Stir in the fresh herbs (parsley and/or dill), along with the lemon juice.
Optionally, for a creamier soup, whisk together tahini with water in a small bowl until the tahini is very fluffy and pourable. Stir this into the soup and allow it to simmer for another minute.
The soup is ready to enjoy! I love to top it with a drizzle of good extra-virgin olive oil.