In a medium bowl, whisk together the harissa paste, olive oil, minced garlic, lemon juice, balsamic vinegar, ground cumin, ground coriander, smoked paprika, ground cardamom, salt, pepper, and ground cinnamon until well combined.

Place the boneless skinless chicken thighs into a large resealable bag or shallow dish. Pour the prepared marinade over the chicken, ensuring each piece is well coated. Seal the bag or cover the dish, and refrigerate for 4 to 24 hours.

In a small bowl, combine Greek yogurt, chopped cilantro, parsley, and additional minced garlic. Mix until the sauce is smooth and the herbs are evenly distributed.

For grilling, preheat your grill to 400-450°F. Grill the marinated chicken thighs for 5-7 minutes on each side, until the internal temperature reaches 170°F.

Once cooked, allow the harissa chicken to rest for 5 minutes before serving, alongside the chilled yogurt sauce.