Bring a large pot of salted water to a boil and set a bowl of ice water nearby. Add the green beans to the boiling water and blanch for 2 minutes. Use a slotted spoon to transfer the beans directly to the ice water and let them cool completely, about 15 seconds. Drain well, then spread on paper towels or a clean kitchen towel to dry.
Add all dressing ingredients to a large glass jar. Season to taste, I usually add 1/2 tsp salt & 1/4 tsp pepper. Seal the jar and shake well until the mayo is fully incorporated and the dressing is smooth. For the best flavor, make the dressing ahead of time and chill. Shake again before using.
In a large bowl, combine the dried green beans, red onion, chickpeas, kidney beans, celery, and parsley. Drizzle the dressing over the salad, adding it to taste. You may not want to use all of it depending on how dressed or marinated you like the salad. Toss well, taste, and adjust seasoning as needed. Enjoy right away or chill before serving.
Notes
Storage: I like this salad best the day it’s made or the next day, but it will keep in an airtight container in the fridge for up to 3 days. Stir before serving. To keep it fresh longer, store the dressing and salad separately, then combine shortly before eating.