Soak the pumpkin seeds in boiling water while you prepare the rest of the soup.
Heat the olive oil in a soup pot over medium heat. Add the onion, celery, broccoli stems, salt, and several grinds of pepper and sauté until softened, about 5 minutes.
Add the beans (or potatoes) and garlic and stir, then add the broth, cover and simmer for 15 minutes to let the flavors develop or the potatoes are tender.
Add the broccoli florets and simmer 5 minutes.
Rinse and drain the pumpkin seeds and put in a blender.
Transfer the soup to the blender. Add the lemon juice, apple cider vinegar and mustard, and blend until creamy. Work in batches, if necessary.
Add the dill and pulse just a few times, so you still see bits of the dill. If the soup is too thick, add a little more broth to get your desired consistency.
Serve garnished with dill and chopped pumpkin seeds.