Ingredients

• 2 large boiling potatoes (1 pound total)
• 3 cups shredded wine-braised chuck roast
• 3 tablespoons red-wine vinegar
• 1 1/2 tablespoons Dijon mustard
• 1/4 cup finely chopped shallots (about 2)
• 3/4 teaspoon sugar
• 1 teaspoon salt
• 1/4 teaspoon black pepper
• 5 tablespoons mild olive or vegetable oil
• 1/2 pound haricots verts or regular green beans, trimmed and halved diagonally
• 1 large head Bibb lettuce
• 6 cornichons (French sour gherkins), cut lengthwise into 1/8-inch-thick matchsticks
• 1/4 cup chopped fresh flat-leaf parsley

Instructions

1. Put oven rack in middle position and preheat oven to 400°F.
2. Place potatoes on a 12-inch square of foil, then prick each with a fork and wrap in foil. Bake until tender, about 1 hour. (Potatoes are done when a small knife pierces centers easily.) Unwrap potatoes and cool slightly.
3. Reheat beef in a small baking dish, covered, in oven or in microwave until warm. While beef is heating, whisk together vinegar, mustard, shallots, sugar, salt, and pepper in a small bowl, then add oil in a slow stream, whisking until dressing is emulsified.
4. Steam beans in a steamer set over boiling water, covered, until just tender, about 5 minutes. Meanwhile, peel potatoes and cut crosswise into 1/4-inch-thick slices, transferring to a large bowl. Add hot beans to warm potatoes along with 2 tablespoons vinaigrette, gently tossing to coat.
5. Line a platter or 4 plates with lettuce leaves and arrange potato mixture on top. Toss meat, cornichons, and parsley with remaining vinaigrette and mound on top of potato mixture.