Place potatoes in large pot, cover with cold salted water by 2 inches. Bring to boil, reduce heat and simmer until tender, 15-20 minutes.

Bring another pot of salted water to boil. Prepare ice bath in large bowl.

Cook green beans in boiling water 3-4 minutes until crisp-tender. Transfer immediately to ice bath.

Drain potatoes and let cool until warm but comfortable to handle. Cut into bite-sized pieces if needed.

Whisk together vinegar and mustard. Gradually whisk in olive oil until emulsified.

Drain green beans thoroughly and pat dry with paper towels.

Combine warm potatoes and green beans in serving bowl. Pour vinaigrette over and toss gently.

Add chopped herbs, season with salt and pepper. Toss gently to distribute herbs.

Let stand at room temperature 30 minutes before serving to allow flavors to meld.

Garnish with hard-boiled eggs if desired and serve at room temperature.