Heat 2 tablespoons of oil in a saucepan, sauté the chopped onion and garlic in it, add the potatoes and celery and sauté. Add the broth, bring to the boil and cover and simmer over low heat for approx. 10 minutes. Pour in the cream and puree the soup with a blender. Season with salt, pepper and lemon zest and fold in the wild garlic.
Heat the remaining oil in a coated pan and roast the onion rings in it. Salt, sprinkle with sugar and caramelize lightly.
Divide the soup in soup bowls and serve garnished with the onion rings.