Peeled and cut the potatoes into ¾-inch cubes.
Place potatoes in a large saucepan and add water to cover by 1-inch. Bring to boil over medium-high heat.
Add 1-tablespoon salt, reduce heat to medium, and simmer. Stir a few times, until potatoes are fork-tender, about 8 minutes.
Drain and transfer to a large bowl.
In a medium-sized bowl whisk together yogurt, mayonnaise, mustard, salt, pepper, and onion powder. Add to the potatoes and gently stir to combine.
Separately, peel and cut the hard-boiled eggs into ¼-inch cubes.
Add celery, pickles, red onions, parsley, and chopped eggs to the potato mixture, stir to combine.
Add more salt and pepper to taste.
Cover and refrigerate until chilled, about 1 hour before serving.
