Whisk all ingredients for vinaigrette except olive and pecan oils, if using. Slowly add oil, continuing to whisk. Set aside.
Combine apples, pecans, cherries and Le Gruyère® cheese in salad bowl. Spoon in part of the vinaigrette, to moisten. Add additional salt, if desired, and toss. Divide mixture on 4 plates. Add mustard greens to salad bowl and toss lightly with small amount of vinaigrette. Pile greens over apple-cheese mixture and serve salads immediately.
*You may substitute pears for apples
** You may substitute watercress or arugula or a mixture of greens.