- In a large saucepan, soften the onions in the oil. Add the radishes and apples and cook gently for about 5 minutes, stirring frequently. Add the broth and potatoes and bring to a boil. Cover and simmer gently for about 20 minutes or until the potatoes are tender.
- In a blender, purée the soup until smooth. Add the cream. Season with salt and pepper. Add broth, if needed.
- Top each toasted bread slice with cheese, slices of radish, and then apple julienne. Soak the apple julienne in lemon juice if it is not being served immediately.
- Ladle the soup into four bowls. Season with pepper and serve with the garnished toasted bread slices.