Raspberry-Balsamic Chicken with Shallots

Combine jam and vinegar in a small pan over medium-low heat. Cook, stirring often, until the jam is dissolved, 3 to 4 minutes. Remove from heat, stir in salt and pepper and let cool slightly. Reserve 1/2 cup of the sauce. Place chicken breasts and the rest of the sauce in a large sealable plastic bag. Seal and shake gently to coat. Marinate in the refrigerator for 1 to 1 1/2 hours. Heat oil in a large nonstick skillet over medium-high heat. Add shallots and thyme and cook, stirring often, until the shallots begin to soften, about 1 minute. Remove the chicken from the marinade (discard marinade). Add the chicken to the pan and cook until just beginning to brown, 2 minutes on each side. Add the reserved raspberry sauce; stir to melt the jam and coat the chicken. Reduce heat to low, cover and cook until the chicken is cooked through and no longer pink in the center, 6 to 10 minutes. Serve immediately.