In a medium bowl, whisk together the bourbon, soy sauce, brown sugar, apple cider vinegar, honey, Dijon mustard, minced garlic, grated ginger, smoked paprika, and red pepper flakes until combined and sugar is dissolved.

Place the chicken thighs in a resealable bag or shallow dish, pour the marinade over, seal tightly, and refrigerate for at least 2 hours or overnight.

Preheat the grill to medium-high heat, around 375°F (190°C), about 20 minutes before grilling.

Remove chicken from marinade, allowing excess to drip off, and set aside the leftover marinade.

Grill chicken thighs for 5-7 minutes on one side, until charred, then flip and grill for another 5-7 minutes or until internal temperature reaches 165°F (75°C).

While the chicken is grilling, heat olive oil in a skillet and sauté sliced onions until golden and caramelized, about 5-7 minutes.

In a saucepan, bring the reserved marinade to a boil, then reduce heat to simmer for about 5 minutes until thickened.

Brush the grilled chicken with the thickened marinade glaze, let rest, then serve topped with caramelized onions, chopped green onions, and sesame seeds.