Whisk first 7 ingredients in large bowl to blend. Season dressing to taste with salt and pepper. (Can be prepared 1 day ahead. Cover and refrigerate. Bring to room temperature before continuing.) Cook potatoes in large pot of boiling salted water until just tender, about 35 minutes. Drain. Return potatoes to pot. Place pot over low heat until liquid from potatoes evaporates, about 2 minutes. Cut warm potatoes into 1/3-inch-thick slices. Add to dressing. Toss gently to coat. Let stand at least 1 hour at room temperature. Toss again and serve.