Place the potatoes in a large pot of salted water and bring to a boil. Reduce the heat and let cook approximately 10 minutes, until the potatoes are cooked through, but still retain their shape. Drain and let cool slightly.

In a small bowl or mason jar with lid, place the olive oil, apple cider vinegar, Dijon mustard, old fashioned mustard, and sea salt and pepper, to taste. Mix or shake until well combined.

Transfer the potatoes to a large mixing bowl. Add the vinaigrette and top with the radishes, the scallions and the tarragon. Mix delicately until the vinaigrette is well distributed. Enjoy right away or store in the fridge until ready to eat. Bon appétit!