- Bring two large pots of salted water to a boil. Plunge the fiddleheads into the first pot and blanch for 1 minute. Drain and discard the water. Repeat with the second pot of boiling water. Plunge the fiddleheads into a bowl of ice water to stop the cooking. Drain and set aside.
- In a large pot over medium heat, soften the leek in the butter for 5 minutes. Season with salt and pepper. Add the fiddleheads and cook for another 5 minutes. Deglaze with the wine and add the broth. Bring to a boil. Cover and simmer for 20 minutes.
- In a blender, purée the soup until smooth. Adjust the seasoning.
- Serve the soup in bowls. Garnish with the 15% cream.