Place the red potatoes in a large pot and cover them with cold water, adding a pinch of salt. Bring to a boil, then simmer for 10-20 minutes until fork-tender. Drain and cool in an ice bath.

While potatoes cool, fill a saucepan with water and place a steamer basket above it. Steam eggs for 15 minutes, then place them in an ice bath to cool.

In a medium bowl, whisk together mayonnaise, sour cream, and Dijon mustard until smooth to create the dressing.

Cut cooled potatoes into bite-sized pieces and chop hard-boiled eggs. In a large bowl, combine potatoes, eggs, celery, onion, dill, and chives, then pour dressing on top and toss gently.

Adjust seasoning with salt and freshly ground black pepper to taste. Serve immediately or refrigerate to let flavors meld before serving.