Green Apple and Celery Salad With Walnuts and Mustard Vinaigrette

VINAIGRETTE
1/4 cup fresh lemon juice
1/4 cup Dijon mustard
5 teaspoons honey
2/3 cup extra-virgin olive oil
SALAD
1 bunch celery & leaves
2 large granny smith apples, peeled, quartered, cored, each quarter cut into 2 wedges, then thinly sliced crosswise into triangle
3/4 cup walnuts, toasted, chopped

Whisk first 3 ingredients in small bowl to blend. Gradually whisk in oil. Season vinaigrette with salt and pepper.
Trim celery leaves and chop enough to measure 1 cup. Thinly slice stalks on deep diagonal. Place celery pieces in bowl of cold water. (Vinaigrette, celery leaves, and celery pieces can be prepared 1 day ahead. Cover separately and refrigerate.).
Drain celery; pat dry with paper towels. Combine celery, celery leaves, apples, and walnuts in large bowl. Add vinaigrette and toss to coat. Season salad to taste with salt and pepper.