Preheat the oven to 350°F.
Trim any excess fat from the chicken thighs. Place all the chicken pieces in a Dutch oven or Magnalite pot.
Drizzle the olive oil over the chicken. Season generously with Creole Trinity and Herb, Cajun seasoning, salt, and pepper, rubbing the seasoning all over and under the skin.
Scatter the sliced onions over the chicken. Sprinkle the au jus gravy mix evenly across the top. Add the sliced pepperoncini peppers and a splash of their jar juice.
In a small bowl, stir together the water and Better Than Bouillon until dissolved. Pour into the pot.
Lay the sliced butter evenly across the top of everything so it melts and distributes during cooking.
Cover and bake at 350°F for 2 hours until the chicken is completely tender, falling off the bone, and the sauce is rich and savory.
Spoon the buttery, tangy gravy generously over the chicken before serving.