In a large bowl, combine soy sauce, hoisin sauce, rice vinegar, honey, five-spice powder, minced garlic, and ginger. Whisk the marinade until well mixed. Add the chicken thighs, ensuring each piece is thoroughly coated in the marinade. Cover the bowl with plastic wrap and refrigerate for at least 30 minutes, but for best flavor, aim for 24 hours.

Preheat your oven to 325°F (165°C) for bone-in thighs, or to 425°F (220°C) for boneless thighs.

Line a baking sheet with parchment paper or aluminum foil to simplify cleanup later.

Take the marinated chicken out of the refrigerator and place it spaced apart on the prepared baking sheet.

Bake the chicken in the preheated oven, basting every 15 minutes with the leftover marinade. Roast for 45-55 minutes for bone-in or 15-18 minutes for boneless, ensuring the thickest part reaches 165°F (75°C).

Once cooked, remove the Char Siu Chicken from the oven and allow it to rest for about 5 minutes. Garnish with freshly sliced green onions and sesame seeds before serving.