Mix the olive oil, shallot, salt, black pepper, green olives, olive brine, capers, and caper brine in a large mixing bowl. Add the prunes, dried oregano, and red wine vinegar; stir to combine.
Add the chicken and toss it until it's completely coated. Cover the bowl with plastic wrap and refrigerate it for 1 hour or overnight.
Preheat the oven to 350˚F. Place the oven rack in the bottom position.
Remove the chicken from the fridge and place it in a large baking dish or roasting pan. Season it with salt and pepper to taste, and pour in the marinade.
Place the sliced onion and quartered garlic in the spaces between the chicken. Add the bay leaves. Sprinkle the chicken with thinly sliced garlic.
Top the chicken thighs and drumsticks with brown sugar. Pour in the wine, chicken broth, and orange juice from the side.
Pop the baking dish into the oven for 45 to 50 minutes or until the chicken is cooked. Use an Instant Read Meat Thermometer to check for doneness - chicken is cooked through when its internal temperature registers at 165˚F.
Remove it from the oven and let it rest for 10 minutes.
Transfer to a platter, baste it with the cooking juices, and serve warm.