Combine the minced garlic, chopped prunes, chopped olives, 2 Tablespoons capers, 2 Tablespoons olive oil, 2 Tablespoons red wine vinegar, 2 bay leaves, and 1 Tablespoon dried oregano together in a 9x9" glass baking dish or similarly sized casserole dish. Add 1 1/2 pounds boneless skinless chicken thighs and toss to coat the chicken. Cover and refrigerate the dish for at least 4 hours or up to overnight to marinate.
Heat oven to 350°F. Sprinkle 2 Tablespoons brown sugar evenly over the chicken and pour 3 Tablespoons water over the top. Bake until the center of the thighs measure 165°F on an instant-read thermometer, 45-60 minutes. Sprinkle with 1 Tablespoon minced fresh parsley, if desired.
Notes
Pitted green olives that are plain, or stuffed with pimento or garlic can be used.