Peel potatoes and cut into small cubes. Peel and dice onion. Clean chanterelle, halve or quarter the large.
Heat butter in a saucepan, sauté onion, add diced potatoes and pour in the soup. Season with bay leaf, thyme, caraway, salt and pepper and bring to a boil.
When the potato cubes are still firm, remove a third and reserve for added to soup. Remove bay leaf and puree the soup with creme fraiche and season.
Fry chanterelles in olive oil briefly, add potatoe cubes and season with salt.