MIXED GREENS: Put the mesclun greens in a large bowl and drizzle with vinaigrette (recipe follows), mixing vinaigrette into the greens with your hand to lightly coat them to taste (you can always add more). Put dressed greens on serving plates and top with a few grinds of black pepper and a sprinkle of Fleur de Sel to taste, if using. Use a knife or cheese shaver to shave cheese into thin shards. Distribute cheese over each salad and serve.
WINE-LOVING VINAIGRETTE: Combine mustard and vinegar in a mixing bowl and whisk to blend. Slowly add 2-3 tablespoons of the oil in a thin stream, whisking constantly until mixture thickens. Add remaining oil in a steady stream, continuing to whisk. Season with salt and pepper to taste.