Heat the olive oil in a saucepan. Add the onion and garlic and sweat for a few minutes.
Add the water and spinach, and stir until the spinach has wilted. Season with salt and freshly ground black pepper, then add the crème fraîche. Heat through completely.
Blend using a small hand blender until smooth. Pass through a sieve into a warm soup bowl and sprinkle with parsley. Serve immediately.