Wash the cucumber, brush it off well and dice it into small pieces. Puree with buttermilk, sour cream and stock in a blender.
Rinse off the herbs and pat dry. Pick up some dill tips. Chop the remaining herbs. Peel and squeeze the garlic. Add chopped herbs and crabs to the soup and season well with salt, pepper and garlic. Finely dice the egg.
Divide the soup into chilled soup bowls and garnish with egg cubes and dill tips.