Drain herring and remove pickling spices. Pat with a paper towel to dry as much as possible.
Place in bowl; add pickle, apple, sour cream and parsley. Stir gently with a rubber spatula. Season with salt and pepper to taste.
Divide mesclun mix and sliced tomatoes among 4 plates. Divide herring salad among plates, on top of the greens.
Serve with German pumpernickel bread or sunflower bread.