Instructions:
Bring a large saucepan of salted water to a boil over high heat. Toss in the haricots verts, and cook for 3 to 5 minutes, until the beans are just tender but still firm. Transfer the beans to large bowl of ice water to stop them from cooking further. Drain and place them in a large bowl.
Whisk together the oil, vinegar, and mustard in a small bowl until the dressing is blended.
Add the mushrooms, shallots and ham to the bowl of haricots verts, and pour the dressing overtop. Season with salt and pepper, tossing gently to coat, and serve at room temperature.