12 ounces haricots verts, (see Ingredient Note) or green beans, stem ends trimmed
2 tablespoons coarsely chopped walnuts
1 1/2 cups cherry tomatoes, halved
2 tablespoons chopped fresh parsley
6 cups mâche, (see Ingredient Note) or Boston lettuce, torn into bite-size pieces
To prepare dressing: Whisk shallot, vinegar, mustard, salt and pepper in a small bowl. Gradually whisk in oil.
Cook haricots verts (or green beans), uncovered, in a large pot of boiling water until crisp-tender; 3 to 4 minutes for haricots verts, 4 to 6 minutes for green beans. Drain, refresh under cold water and pat dry.
Toast walnuts in a small dry skillet over medium-low heat, stirring constantly, until fragrant, 2 to 3 minutes. Transfer to a small bowl to cool.
To prepare salad: Combine the beans, tomatoes and parsley in a large bowl. Toss with the dressing. Divide m&acirc;che (or lettuce) among 6 salad plates. Spoon bean mixture onto the greens, sprinkle with the walnuts and serve.