Step 1Boil the potatoes, beets and carrots in separate pots until tender. Drain. Peel and dice the potatoes and beets. Place all the vegetables in a large bowl to cool.
Step 2Add the celery, onion, pickle relish and parsley and mix.
Step 3Combine the mayonnaise, vinegar, olive oil, mustard, salt and pepper. Add to the salad and mix gently with a rubber spatula. Refrigerate the salad for several hours and mix again. The salad tastes best if prepared the night before serving.