Wash the small new potatoes thoroughly under cool water and cut them into evenly-sized pieces (quarters for larger ones).

In a pot, bring salted water to a boil and add the potatoes. Cook for 15–20 minutes until just tender but not falling apart.

Drain the potatoes in a colander and let them sit for a few minutes to reduce excess moisture. Set aside to cool slightly.

In a medium bowl, whisk together the olive oil, vinegar, Dijon mustard, and minced garlic until emulsified. Adjust seasoning with salt and pepper.

While the potatoes are still warm, toss them gently with the herb vinaigrette. Add the freshly chopped parsley, dill, chives, and optional diced red onion.

Taste and adjust the seasoning with extra salt or a squeeze of fresh lemon juice if needed.

Serve immediately or chill in the refrigerator for about 30 minutes before serving.