Ingredients :

• Sweet onions — The centerpiece. Use Walla Walla or Vidalia if you can find them — they have a natural sweetness that prevents the soup from being too sharp. Classic yellow onions also work, but expect a slightly stronger taste. You’ll need about 450g, or 2 large onions.
• Celery — Three stalks provide the base aroma. It completely disappears in the blender, but without it, the soup lacks body. Cut it fine enough so it cooks at the same rate as the onions.
• Chicken broth — Three cups. Use what you have — homemade, cubes, or carton. If your broth is already quite salty, go easy on the final seasoning. Vegetable broth works great too if you want a vegetarian version.
• Heavy cream — Don’t use low-fat cream here, it’s not worth it. Full-fat cream provides that silky texture that makes all the difference. Three quarters of a cup is rich without being heavy.