In a large bowl, combine the chicken pieces with olive oil, garlic powder, smoked paprika, salt, and pepper. Cover and refrigerate for at least 30 minutes to marinate.
If using bamboo skewers, soak them in water for 30 minutes. Thread the marinated chicken onto skewers.
Preheat a grill or grill pan over medium-high heat. Grill chicken skewers for 4–5 minutes per side, or until nicely charred and cooked through.
While the chicken is cooking, whisk together all ingredients for the bang bang sauce in a small bowl until smooth and creamy.
Drizzle the sauce over the grilled chicken skewers or serve it on the side for dipping. Garnish with sliced green onions or sesame seeds if desired.