In a large soup pot over medium heat, sauté the leek, onion, carrot, celery, squash, and pepper in the olive oil until the squash begins to soften, about 10 minutes. Stir the vegetables fairly often, but allow a nice fond to develop on the bottom of the pan. The term fond is typically applied to browning meat in a pan, but I'm referring here to the brown residue from the vegetables that is deposited on the bottom of the pan. This is a fantastic building block of flavor to anything, and is a key component to developing a rich vegetable flavor in this soup.
Add the garlic, thyme, oregano, salt, and pepper. Sauté another 5 minutes until fragrant.
Add the vegetable broth and Parmesan cheese rind. This is a wonderful use for the rind, as it adds just a hint of a cheese flavor. Simmer for 10 minutes to concentrate the flavors a bit.
Add the beans, cooked chicken, and harissa. I just buy one half of a pre-roasted chicken at the market for this, and shred the meat of one breast. Simmer for 10 minutes.
Roast the tomatoes at 425˚F and remove the peel. Coarsely chop and add to the soup along with the spinach leaves. Alternatively, the tomatoes can be dropped into boiling water for 10 seconds and then peeled.
Using an immersible blender, whirl the soup for about 15 seconds to puree a little of the soup. Alternatively, remove 2 cups of the soup from the pot, throw it in a blender, and stir it back into the soup.
Serve hot with a shaving of parmesan cheese on top, along with a hunk of bread slathered with butter.