In a heavy saucepan, heat olive oil over medium heat. Add onion; sauté until tender, 3 to 4 minutes. Add garlic; sauté for 1 minute. Add watercress; sauté for 1 minute. Stir in chicken broth; cook for 5 minutes, stirring occasionally.
Purée using an immersion blender, or process in batches in the container of a blender.
Return to heat, and add cream, Crème Fraîche, cheese, salt, and pepper. Cook, stirring frequently, until thoroughly heated. Garnish with Crème Fraîche and watercress, if desired.
Notes
*Sour cream may be substituted for Crème Fraîche.
Recipe by Victoria at https://victoriamag.com/watercress-bisque-creme-fraiche-recipe/