Prepare the green beans by washing and trimming them, then blanch in boiling water for 2-3 minutes until vibrant green. Transfer to ice bath.

While the beans cool, drain and rinse the kidney beans and chickpeas, and finely chop the red onion, bell pepper, and celery.

In a small mixing bowl, whisk together olive oil, apple cider vinegar, and Dijon mustard until emulsified. Season with salt and pepper to taste.

In a large mixing bowl, combine the cooled green beans, kidney beans, and chickpeas with the chopped vegetables. Toss gently to mix.

Drizzle the dressing over the salad mixture and toss gently to coat. Avoid overmixing to maintain integrity.

Before serving, sprinkle with parsley or cilantro and optional feta cheese. Let sit for 30 minutes to allow flavors to meld.