Clean, wash and drain the salad and pluck into bite-sized pieces. Wash the grapes. Halve the blue grapes and remove seeds. Slice cheese into thin slices with a cheese slicer. Stir mayonnaise, yoghurt and orange juice until smooth.
Season to taste with salt, pepper and sherry. Chop the walnuts. Arrange prepared ingredients on plates. Pour sauce over them and sprinkle with walnuts.