Place cubed potatoes in a large pot, cover with water, and add a pinch of salt.
Bring to a boil, then reduce heat and simmer for 10–12 minutes until tender but firm. Drain and let cool slightly.
In a mixing bowl, whisk together mayonnaise, mustard, vinegar, salt, and pepper.
Add the cooled potatoes, red onion, celery, and herbs to the dressing. Gently toss to coat.
Fold in hard-boiled eggs (if using).
Refrigerate for at least 1 hour before serving to allow flavors to meld.
Garnish with extra herbs or paprika before serving.
