Cook the red potatoes in a large pot covered with cold water and a pinch of salt. Bring to a boil, then simmer for 10-20 minutes until fork-tender. Drain and plunge into an ice bath.

Prepare eggs by steaming in a basket over boiling water for 15 minutes, then cool in an ice bath.

In a bowl, mix mayonnaise, sour cream, and Dijon mustard until smooth.

Chop cooled potatoes and eggs. In a bowl, fold potatoes, eggs, celery, red onion, dill, and chives together.

Add dressing to the potato mixture and toss gently. Season with salt and pepper to taste.

Cover and chill in the refrigerator for at least 30 minutes before serving. Adjust seasoning and garnish with additional chives or dill.