Beet Potato Salad

3/4 pound potatoes
2  large beets, roasted
1  celery rib, diced
½  small onion, minced
2  hard-boiled eggs, peeled and finely chopped
2  tablespoons minced parsely
2  tablespoons white wine vinegar
 Salt to taste
2  teaspoons Dijon mustard
1/2  cup mayonnaise
Freshly ground pepper

Cut the potatoes into halves or quarters and steam over 1 inch of boiling water until tender, 15 to 20 minutes. Remove from the heat. When they are cool enough to handle, cut in small dice.
Peel the beets and cut in small dice. In a large bowl, combine with the potatoes, celery, onion, hard-boiled eggs and chives.
In a small bowl or measuring cup, whisk together the vinegar, mustard and salt. Whisk in the olive oil and the yogurt. Toss with the vegetables. Add freshly ground pepper, taste and adjust salt. Serve right away or refrigerate.