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