Place the potatoes in a small pot and cover them with water.
Season with salt, cover, and boil until fork-tender, about6 minutes.
Drain and cool.
Meanwhile, pulse the chives, tarragon, vinegar, yogurt, 1/2 teaspoon salt, and pepper to taste in a food processor.
Slowly drizzle in the olive oil and pulse to make a thick dressing.
Toss the romaine, potatoes, chicken, cucumber, radishes, and bell pepper with the dressing in a large bowl.
Season with salt and pepper.