Step 1: In a medium bowl, whisk together the pineapple juice, soy sauce, brown sugar, ketchup, chicken broth, ginger, garlic, and sesame oil until the sugar is fully dissolved.
Step 2: Reserve 1 cup of the marinade in a separate container and refrigerate; this will be used for basting later.
Step 3: Place the chicken thighs in a large resealable bag or glass container and pour the remaining marinade over them. Seal and refrigerate for at least 4 hours, or up to 24 hours for best flavor.
Step 4: Preheat your grill to medium heat (about 350-375°F) and lightly oil the grates.
Step 5: Remove the chicken from the marinade and discard the liquid used for soaking. Place the chicken on the grill, skin-side down.
Step 6: Grill the chicken for about 20-25 minutes, turning (huli!) every 5 minutes to ensure even cooking and to prevent the skin from burning.
Step 7: During the final 10 minutes of grilling, begin basting the chicken generously with the reserved marinade every time you flip it.
Step 8: Cook until the internal temperature reaches 165°F (74°C). Remove from the grill and let rest for 5 minutes.
Step 9: Garnish with green onions and sesame seeds if desired, and serve immediately with extra glaze.