If using wooden skewers, soak them in water for at least 30 minutes to prevent burning.
In a medium bowl, whisk together the yogurt, butter, garlic, lemon zest and juice, olive oil, cumin, coriander, salt, and black pepper.
Add the chicken pieces to the marinade and toss to coat thoroughly.
Cover and refrigerate for at least 2 hours, preferably overnight.
Preheat your grill to medium-high heat.
Thread the marinated chicken onto the skewers.
Grill the skewers for 5 - 7 minutes on each side, or until the chicken is cooked through and nicely charred.
Transfer to a serving plate and brush with extra melted butter.
Finish with a squeeze of fresh lemon juice and a sprinkle of chopped cilantro or parsley.