1. Trim the asparagus, reserving the tips for later. Cut the stems into 2.5 cm (1-inch) pieces.

2. Melt the butter in a large pot over medium heat. Add the chopped onion and asparagus stems. Sauté until the onion is translucent, about 15 minutes.

3. Add the water and vegetable broth cube. Bring to a boil, then reduce heat and simmer for 10 minutes.

4. Blend the soup with an immersion blender until smooth. If using a countertop blender, carefully transfer in batches, blend, then return to the pot.

5. Stir in the heavy cream and crème fraîche. Keep warm over low heat.

6. Meanwhile, bring a small pot of salted water to a boil. Add the reserved asparagus tips and cook for 2 minutes. Drain and set aside.

7. Season the soup with salt and pepper. Stir in the chopped parsley and add the cooked asparagus tips. Serve immediately with crusty bread if desired.