This is adapted and updated for 21st century palates, from a recipe for "Dutch Salad" in the 1960 edition of Mrs. Beeton's Book of Household Management. The old version is a chopped salad with (gasp!) mayo dressing and Romaine lettuce bed: I livened and freshened up the ingredients and arrangement. If you're a herring fan, you'll love this: it's sweet, tangy, and a tiny bit spicy. —celiaruthless
Boil the potatoes until tender (about 20 minutes), rinse in cold water, and slice thin. Simmer the beets until done (about 20 minutes - or microwave, covered, for 6), rinse in cold water, and slice thin.
Arrange the potatoes, beets, apple, pickles, and herring on top of the arugula. Sprinkle chopped onion on top.
Whisk all dressing ingredients together in a small bowl, drizzle dressing over the salad, and serve.