Warm Potato and Watercress Salad

Directions

Position a rack in the centre of the oven and heat the oven to 400°F. On a large rimmed baking sheet, toss the potatoes with 1 Tbs. of the oil and 1/2 tsp. salt. Roast, tossing occasionally, until golden brown and tender, about 20 minutes. Meanwhile, in a small bowl, whisk the vinegar, mustard, and 1/4 tsp. salt. Whisking constantly, slowly pour in the remaining 4 Tbs. olive oil to form a thick dressing. Pour half of the dressing directly over the hot potatoes on the baking sheet. Add the watercress and toss until the potatoes absorb the dressing and the watercress starts to wilt. Season to taste with additional salt and pepper. Serve with the remaining dressing on the side.