To make the dressing: In a small bowl, whisk together the dressing ingredients until blended.Preheat an oven to 400ºF.In a bowl, combine the potatoes, olive oil, salt and pepper and toss to coat.
Transfer to a baking sheet or a small roasting pan and roast until the potatoes are tender, golden and crisp, about 45 minutes.
Cut the spears diagonally into 1-inch lengths.
Place in a steamer rack over boiling water, cover the steamer and cook until tender-crisp, about 3 minutes.
Remove the rack from the pan and rinse the asparagus under running cold water until cool.In a large bowl, combine the potatoes, asparagus, arugula and dressing, to taste, and toss to mix. Divide the salad among individual plates.
