In small saucepan, combine vinegar and water. Add sugar and Pickling Spice.
Bring to a boil, stirring to dissolve sugar. Boil 2 minutes; cool. Strain and discard spices. Cut herring fillets in 1/2"-wide strips and place in a shallow dish. Pour cold marinade over fish. Cover and marinate several hours or overnight.
Drain herring strips. In a bowl, combine sour cream, mayonnaise, mustard and onion. Cut apples in fourths, remove cores and slice thinly (do not peel). Add sliced apples and herrings to sour cream mixture and mix together gently until coated with dressing. Arrange lettuce leaves on 4 plates. Spoon herring mixture on plates and garnish with green onion daisies and dill sprigs, if desired. Serve chilled.