Bring a large pot of salted water to a boil and cook the potatoes until fork-tender, about 15–20 minutes.
Drain the potatoes and allow them to cool slightly.
In a large bowl, whisk together the Greek yogurt, Dijon mustard, lemon juice, olive oil, salt, and black pepper.
Add the warm potatoes to the bowl and gently toss until evenly coated.
Stir in the green onions, chives, and parsley.
Taste and adjust seasoning if needed.
Allow the salad to rest for 10 minutes before serving so the flavors can blend together.
Serve warm or chilled.