Preheat a small skillet over medium heat. Add the pecans and toast, stirring frequently, until fragrant and slightly darker, about 3–4 minutes. Transfer to a plate to cool.

Prepare dressing

In a large mixing bowl combine mayonnaise, Greek yogurt, curry powder, Dijon mustard, honey, lemon juice, 2 teaspoons salt, and 1/4 teaspoon black pepper. Whisk until smooth and taste; adjust curry, salt, or honey to preference.

Combine salad ingredients

Add the shredded chicken, chopped celery, diced red onion, halved grapes, diced apple, sliced pickles, and cooled chopped pecans to the bowl with the dressing. Gently fold until everything is evenly coated. Refrigerate for at least 15 minutes to let flavors meld. Taste and adjust seasoning, adding up to 1 additional teaspoon salt or more black pepper if needed.

Assembly & Bread

Toast bread

Lightly butter the pumpernickel slices if desired. Toast slices in a toaster or under a broiler until crisp and warmed through. If using a pan, toast 1 teaspoon butter per side in a skillet over medium heat until edges are golden, about 1–2 minutes per side.

Assemble sandwiches

Lay out 6 toasted pumpernickel slices. Top each with about 1/2 cup curried chicken salad (adjust to preference). Divide arugula among sandwiches (about 2/3 cup per sandwich) and place on top of the chicken salad. Close sandwiches with remaining bread slices. Cut each sandwich in half on the diagonal and serve immediately.

Bistro Fries (side)

Bake or air-fry fries

Preheat oven to 220°C (430°F) or preheat air fryer per manufacturer's instructions. Toss frozen fries with olive oil, smoked paprika, remaining 1 teaspoon salt, and remaining 1/4 teaspoon pepper. Spread in a single layer on a rimmed baking sheet (or air fryer basket). Bake for 20–25 minutes, turning once halfway, until golden and crisp; or air-fry at 200°C (400°F) for 12–16 minutes, shaking basket halfway.

Serve

Portion fries alongside each sandwich. Optionally sprinkle a pinch more salt or chopped parsley over fries before serving.