1In small bowl, mix preserves, vinegar and liqueur; set aside.
2Between pieces of plastic wrap or waxed paper, place each chicken breast smooth side down; gently pound with flat side of meat mallet or rolling pin until about 1/4 inch thick. Sprinkle chicken on both sides with thyme, salt and pepper.
3In large skillet, heat oil over medium-high heat. Cook onion in oil about 3 minutes, stirring frequently, until softened. Add chicken; cook 8 to 10 minutes, turning once, until no longer pink in center. Remove chicken to plate; cover to keep warm.
4Leave onion in skillet. Add preserves mixture; cook 1 to 2 minutes, stirring constantly, until thickened. Spoon sauce over chicken. Top with raspberries.