Step 1

Place the potatoes in a large pot and cover with water. Bring to a boil over high heat, then reduce to a simmer and cook until potatoes are fork tender. Drain the potatoes and set aside to cool for about 15 minutes.

Step 2

In a large bowl, whisk to combine the diced onion, mayo, sour cream, vinegar, mustard, salt, pepper, celery seed, and dill. Gently stir in the potatoes.

Step 3

Cover and refrigerate for at least 2 hours before serving. Garnish with fresh parsley before serving, if desired.