Peel the potatoes and cut into small cubes, as well as the onion. Cut the cauliflower into small florets.
Sweat the onion in 1 tablespoon of oil. Add cauliflower and potatoes. Pour the vegetable stock and cook over medium heat. Take out a few cauliflower florets and set them aside. Pour off the stock and collect it. Puree the rest with the hand blender. If the soup seems a bit too thick, you can add a little more of the cooking liquid. Add the cream and season with salt and pepper.
Roast pine or sunflower seeds.
Pluck the parsley leaves from the stems and puree with lemon and the remaining rapeseed oil. Season to taste with salt and pepper.
Pour the soup into the plates, add the cauliflower florets, drizzle with parsley oil and sprinkle with the seeds.