Mix together the olive oil, minced garlic, oregano, prunes, capers, 1-½ tablespoons of the brown sugar, bay leaves, olives, and ¼ cup of the white wine.
Place the chicken and the sliced onions in a large storage bag and pour the marinade over the chicken then seal the bag.
Lay the bag flat inside a baking dish to catch any leaks. Work the marinade around the chicken to coat well.
Refrigerate for at least 30 minutes or overnight, turning periodically to keep the chicken covered in the marinade.
About 30 to 45 minutes before you’re ready to roast lightly spray a roasting pan with a cooking spray. Remove the onions from the marinade and spread them out across the bottom of the pan. Place the chicken on top of the onions and season with the kosher salt and black pepper.
Sprinkle the remaining 2 tablespoons of brown sugar on top of each chicken breast, gently pressing it onto the chicken. Reserve the marinade.
Pour the remaining ¼ cup white wine into the pan and roast in a 375-degree oven for 45 minutes.
Add the reserved marinade with the capers, olives and prunes to the pan along with the almonds. Continue to roast for another 10 to 15 minutes or until the thickest part of the chicken reaches 165-degrees and the juices run clear.
Turn the oven to broil and cook for an additional 2 to 3 minutes to crisp the skin of the chicken and toast the almonds.
Serve over creamy mashed potatoes and top with the prunes, capers, olives, toasted almonds and the pan sauce.