This popular dish carries a long Finnish tradition. It was first enjoyed in 18th century in upper-class homes, spreading to the common people in the 19th century.
In a large enough bowl combine the diced potatoes, apples, carrots, onion, dill pickles and herring. Sprinkle on the pepper and dill and combine to evenly distribute the ingredients.
Reserve the diced beets to toss them in just before serving.
Prepare the dressing in a separate bowl by combining all the ingredients and mixing until homogenous.
Now either add it to the salad and toss to coat everything in the dressing. Alternatively, you can serve the dressing on the side so everyone can add as much as they like to their serving.
Keep chilled in the refrigerator. When it's time to serve, add the beet and toss gently. Then, transfer to a serving bowl on a bed or fresh lettuce.