Prepare and cook beans according to packet directions. Drain and set aside.
Heat olive oil in a large saucepan over medium heat. Add the leek and celery and cook, stirring, for 6 - 7 minutes or until softened. Add the garlic and cook, stirring, for 1 minute or until fragrant.
Add the cauliflower, stock and beans. Bring to the boil, reduce heat to low and simmer for 10 minutes or until the cauliflower is tender. Set aside to cool slightly.
Blend the cauliflower mixture in batches until smooth and creamy. Return the soup to a clean saucepan and heat over medium heat until warmed through. Stir in the parmesan and season to taste with salt and pepper.