Waldorf Salad Without Mayo

Preheat the convection/fan oven to 180 °C. Place 200 g walnuts in a bowl and add 1 egg white. Mix until evenly coated, then add 50 g sugar, 1 teaspoon chili powder, 1 teaspoon paprika, 1 teaspoon ground cumin, and 1 teaspoon fennel seeds. Toss to coat, spread on a baking sheet, and bake for 10 minutes. Set aside to cool completely while you prepare and chill the salad.
Thinly slice 2 celery stalks into strips and place them in a large bowl.
Fill another bowl with enough water to cover the apple slices and mix in 1 tablespoon lemon juice. Thinly slice 2 apples, using a mandoline or a sharp knife, and place the slices in the lemon water. Lift them out, drain well, cut into thin strips, and add to the celery.
In a separate bowl, mix 150 g Greek yogurt, 150 g crème fraîche, 1 teaspoon ground white pepper, and 1 tablespoon lemon juice until smooth. Pour over the apples and celery, toss to coat, and refrigerate for 30 minutes.
Just before serving, halve 12 grapes. Divide the chilled apple and celery mixture among four plates and arrange the grapes around it.
Roughly chop the cooled spiced walnuts, reserving a few whole pieces for garnish. Divide the entire walnut batch among the four servings, sprinkling the chopped walnuts over the salad and arranging the reserved pieces around the plates.