Season both sides of the chicken thighs with salt and pepper. Then place them in a gallon-sized Ziploc bag.
In a medium mixing bowl, whisk together the pineapple juice, soy sauce, ketchup, brown sugar, chicken broth, garlic, ginger, and mustard powder until combined.
Pour 3/4 of the sauce into the bag with the chicken. Cover and reserve the remaining sauce in the fridge. Close the Ziploc bag (be sure to remove excess air), smush the marinade onto the chicken, and then refrigerate for 3 to 4 hours or overnight.
Preheat the grill to medium heat. Once hot, oil the grates.
Remove the chicken from the marinade and place on the hot grill. Cook for 4 minutes per side. Once both sides have been grilled, start basting the chicken with the reserved marinade. Continue to turn the chicken every 1-2 minutes, basting with each turn, until the chicken is no longer pink and the internal temperature is 165 degrees F (about 15-16 minutes total).
Remove the chicken to a serving platter. Sprinkle sliced green onions over top and serve warm. We like to serve this chicken with cooked white rice and macaroni salad.
Video
Notes
This recipe can easily be doubled or tripled to serve a larger crowd.