Wash the dill, shake dry, pluck the pennants and cut finely. Mix sour cream and salad cream. Season salad dressing with vinegar, salt and pepper. Stir in dill.
Clean, peel and wash the celery. First cut into thin slices, then into fine strips. Wash the apple and cut it into thin slices all around the core. Cut apple slices into strips.
Mix celery and apple with salad dressing. Halve the avocado, remove the core and peel the flesh. Cut into cubes and fold into the salad.
Rinse crabs cold, drain. Season salad to taste again just before serving. Sprinkle with prawns. Serve with farmhouse bread.