Heat up the olive oil in a pot over a medium-low flame. Add in the diced onion and saute for 2 minutes, or until translucent. Add in the garlic and celery and cook for an additional 3 minutes, stirring occasionally. Add in the beans, parsnip, and vegetable stock. Bring to a boil, lower the flame to medium and cook for 20-25 minutes, until the parsnip is soft.. Transfer the soup to a blender and puree. Season with salt and pepper to taste. Just before serving, top with shaved Parmesan.
I wait until the end to season the soup because some brands are saltier than others.