Ingredients

Makes 6 servings

　　2 1/2 pound sweet potatoes (2 large)

　　1 tablespoon Dijon mustard

　　4 teaspoons white-wine vinegar

　　1/4 teaspoon salt

　　1/4 cup olive oil

　　4 scallions, thinly sliced

　　

Step 1

Peel potatoes and halve lengthwise. Cut lengthwise into 3/4-inch-thick wedges, then cut wedges crosswise into 1-inch pieces. Steam potatoes in a steamer over boiling water in a large pot, covered, until just tender, 10 to 12 minutes.

　　

Step 2

While potatoes steam, whisk together mustard, vinegar, and salt in a large bowl, then add oil in a slow stream, whisking until emulsified.

　　

Step 3

Add hot potatoes to dressing and gently toss to combine well. Cool salad to room temperature, about 15 minutes. Add scallions and salt to taste and gently toss.

　　Cooks' note:

　　Salad (without scallions) can be made 2 hours ahead. Toss in scallions just before serving.