Prepare an ice water bath in a large bowl with ice and cold water.

Bring a large pot of salted water to a boil, then blanch the trimmed green beans for 1-2 minutes.

Transfer the blanched green beans into the ice water bath for about 5 minutes to cool.

Drain the green beans in a colander and set aside.

In the same pot, add halved small white potatoes, cover with water, and bring to a boil.

Reduce heat and simmer the potatoes for 15-20 minutes until fork-tender, then drain and let cool slightly.

In a mixing bowl, whisk together balsamic vinegar, Dijon mustard, minced garlic, and salt.

Drizzle in olive oil while whisking to emulsify the dressing until smooth.

In a large bowl, gently combine cooled potatoes and blanched green beans.

Drizzle the balsamic vinaigrette over the combined mixture and toss gently to coat.

Garnish with freshly chopped chives and cracked black pepper before serving.