– Add the sliced celery, celery leaves, fennel, and apple to a large bowl. Toss to combine.
– In a small bowl, whisk the Dijon mustard, honey, lemon juice, olive oil, salt, and pepper until combined.
– Pour the vinaigrette over the salad and toss to coat. Taste and add more salt and pepper as needed. – To serve, transfer the salad to a serving bowl or platter. Scatter the nuts, cheese (if using), and some torn fennel tops over the salad. This salad is best if eaten right after it’s assembled.