Wash the basil and shake dry.
Put the Parmesan, the pine nuts and a little kefir into a blender and puree well.
Then add the basil leaves and 3-4 tbsp kefir and puree briefly.
Add to the remaining kefir, mix and season to taste with salt and pepper.
Peel the radish and slice very thinly, using a mandoline slicer if available.
Sprinkle with salt and leave to stand for about 10 minutes to draw off some of the moisture.
Ladle the soup into bowls and garnish with radish slices and basil leaves.
Shave a little Parmesan over and serve.
Serve with fresh white bread.