In a small mixing bowl, whisk together mayonnaise, Greek yogurt, honey, apple cider vinegar, poppy seeds, and salt and pepper until smooth. Set aside.

In a large salad bowl, combine mixed salad greens and diced chicken breast. Add sliced strawberries, blueberries, pecans or walnuts, and red onion. Toss gently.

Crumble feta cheese over the salad if desired.

Pour the dressing over the salad and toss until well coated.

Serve immediately for maximum freshness.