Step 1

Place the chopped red onion in a small bowl and cover with cold water to mellow its sharpness. Set aside.

Add the new potatoes to a large pot of generously salted water. Bring to a boil over high heat.

Step 2

Reduce heat to a gentle simmer and cook for about 10 minutes, or until the potatoes are fork-tender. Drain well and transfer to a large mixing bowl while still warm.

Step 3

Gently toss the warm potatoes with rice vinegar, 1/4 teaspoon salt, and 1/2 teaspoon freshly ground black pepper. Add chives, drained red onion, and chopped arugula. Stir gently to combine.

Step 4

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

Pour the vinaigrette over the potato mixture and toss gently until evenly coated. Serve warm or at room temperature.