Makes: 12 servings. Prep: 15 minutes, plus cooling time. Cook: 12 to 15 minutes.
Bring a medium-size pot of water to a boil; salt it. Scrub potatoes and cut them into bite-size pieces; cook them in the water until tender but still firm and not at all mushy, 12 to 15 minutes or so. Drain.
Mix together the mustards, oil, vinegar and basil; toss with the potatoes. Season with salt and pepper. Serve warm or at room temperature.