Boil the red potatoes in a large pot with cold water and a pinch of salt. Bring to a boil, then simmer for 10-20 minutes until tender. Drain and cool.

Transfer the potatoes to an ice bath for 5-10 minutes to halt cooking and maintain texture.

Steam the eggs for 15 minutes in a steamer basket, then place in an ice bath to stop cooking.

Mix mayonnaise, sour cream, and Dijon mustard in a bowl until smooth.

Chop the cooled potatoes and eggs, and combine with celery, red onion, dill, and chives in a large bowl.

Pour the dressing over the mixture and gently toss until coated. Adjust seasoning if needed.

Chill in the refrigerator for at least 30 minutes before serving.