Prepare an ice bath by filling a medium bowl with ice water and set aside.

Bring a large pot of salted water to a rolling boil. Blanch the green beans for 3-4 minutes, and then shock them in the ice bath.

In the same pot, boil the small waxy potatoes for 15-20 minutes until fork-tender. Drain and let cool for 15 minutes.

Once cooled, slice the potatoes in half lengthwise and set aside.

In a small bowl, whisk together balsamic vinegar, Dijon mustard, minced garlic, and salt. Gradually add olive oil while whisking until emulsified.

In a large bowl, combine the halved potatoes and drained green beans. Pour the dressing over and gently toss to coat.

Garnish with chives and black pepper. Chill for 30 minutes or serve immediately.