1. Preheat oven to 400°.
2. Combine first 5 ingredients in a bowl; stir in 1 tablespoon vinegar.
3. Sprinkle lamb with 1/4 teaspoon salt and 1/4 teaspoon pepper. Heat a large ovenproof skillet over medium-high heat. Coat pan with cooking spray. Add lamb to pan; cook for 2 minutes on each side or until browned. Remove lamb from pan; pat thyme mixture over lamb. Return lamb to pan; place pan in oven. Bake at 400° for 15 minutes or until a thermometer registers 138°. Remove lamb from pan, and let stand for 10 minutes. Cut into chops.
4. Return pan to medium-high heat; add remaining 1/4 cup vinegar, port, and shallots. Bring to a boil. Boil 1 minute or until mixture is reduced by half; stir in broth. Bring to a boil; cook 3 minutes or until liquid measures about 1/2 cup. Stir in remaining 1/4 teaspoon salt, remaining 1/4 teaspoon pepper, and preserves. Cook 1 minute; remove from heat. Add butter, stirring until butter melts. Serve sauce with lamb.