01 - In a small bowl, whisk together the olive oil, lemon juice, honey, Dijon mustard, minced garlic, salt, and pepper until well combined. Reserve half of the mixture for dressing the salad and use the remaining half to marinate the chicken.
02 - Place the chicken breasts in a shallow dish or resealable plastic bag. Pour half the marinade over the chicken, turning to coat evenly. Allow to marinate for at least 15 minutes at room temperature, or refrigerate for up to 2 hours for more pronounced flavor.
03 - Preheat an outdoor grill or grill pan over medium-high heat. Lightly brush the cut sides of the nectarine halves with olive oil to prevent sticking.
04 - Grill the marinated chicken breasts for 6 to 7 minutes per side, until fully cooked through and the internal temperature reaches 165°F. Transfer to a plate and let rest for 5 minutes before slicing against the grain.
05 - While the chicken rests, place the nectarine halves cut-side down on the grill. Cook for 3 to 4 minutes until distinct grill marks form and the fruit softens slightly. Slice each half into wedges and set aside.
06 - Place the chopped kale in a large bowl and sprinkle with a pinch of salt. Using your hands, massage the leaves firmly for 1 to 2 minutes until they become tender, wilted, and bright green.
07 - Add the cherry tomatoes, cucumber, red onion, torn basil, torn mint, and half the toasted nuts to the massaged kale. Drizzle with the reserved dressing and toss gently to combine and evenly coat all ingredients.
08 - Arrange the dressed salad on a large serving platter or individual bowls. Top with the sliced grilled chicken, grilled nectarine wedges, crumbled feta cheese if using, and the remaining toasted nuts. Serve immediately while the chicken and nectarines are still warm.