Here is a reimagined version of the Waldorf salad as originally conceived here at the Waldorf Astoria New York. This is a bit lighter and healthier to fit the palate of a modern-day diner — a new spin for a new century.
Preheat the oven to 350 degrees and line a nonstick baking sheet with parchment paper.
In a large bowl, combine the walnuts and egg white. Add the spice mixture and sugar and mix until evenly coated. Spread the walnuts into an even layer on the baking sheet and roast in the oven until browned, about 20 minutes.
In a medium-sized bowl, combine the crème fraîche with the yogurt and whisk in the lemon juice, white pepper, to taste, and truffles, if desired. Add in walnut oil, whisking briskly to emulsify. Set aside.
Using a mandoline on the fine comb setting or a sharp knife, julienne the celery root and apples into matchstick-sized strips, being careful to avoid the seeds in the cores of the apples. Transfer to a mixing bowl. Gently fold the dressing into the apple mixture until well combined.
Divide the salad between chilled serving plates. Garnish with microgreens or celery leaves. Scatter alternating grape halves and candied walnut halves on the plates.