In a large pot over medium heat, add olive oil and butter and then start sautéeing the chopped leek, celery, the white/light green parts of the green onion and the chopped broccoli stems. Season with salt and pepper and continue to sweat down for about 5 minutes.
Add in the chopped garlic and white beans, stir, and then add in the vegetable stock. Bring to a bubble, add in the broccoli florets, and simmer until tender (about 10 minutes), partially covered.
Meanwhile, boil a smaller pot of water and cook the tortellini according to package instructions. Reserve the pasta water and strain the tortellini - keep on the side to add to the soup later.
Toss in the kale, the green parts of the green onion and celery leaves then cook until just slightly wilted but still vibrant in colour (a minute or two).
Transfer to a blender, add fresh basil, and blend until smooth. Use some of the pasta water to thin out the soup slightly until you reach your desired consistency.
Pour back into the pot over low heat. Taste the soup at this point and adjust salt & pepper levels, and a squeeze of lemon to brighten it up. Add in the cooked tortellini and stir to combine.
Serve with a drizzle of cream, lots of shaved parmesan and more basil.