Salad: Asparagus and Mushroom Salad with Parmesan

From Gourmet Magazine:

1 pound med-to-thick asparagus, trimmed
1/2 pound mushrooms, stems trimmed even with caps
4 medium radishes, halved lengthwise and sliced thin crosswise
2 T fresh lemon juice
2 t Dijon mustard
1/2 t salt
1/3 cup extra virgin olive oil
Freshly ground black pepper
1 bunch watercress, coarse stems discarded (I used mache)
1/4 pound piece Parmesan, room temp

With a sharp knife, cut asparagus diagonally into very thin slices and transfer to large bowl. Halve large mushrooms, slice all very thin and add with radishes to asparagus. Toss gently. In a small bowl, whisk together lemon juice, mustard, and salt. Add oil in a stream, whisking, and whisk until emulsified. Drizzle dressing over asparagus and toss gently. Grind pepper over salad. Spread watercress on a platter and top with salad. With a vegetable peeler, shave 1/2 to 3/4 of Parmesan into curls over salad. Serves 6.