1. Melt butter in a deep, large skillet over medium-high heat. Add pork; cook 6 minutes, browning on all sides. Remove pork from pan; set aside, and keep warm.
2. Reduce heat to medium. Add onion; cook 3 minutes. Combine cider and mustard. Add cider mixture, apple, and next 3 ingredients to pan, scraping pan to loosen browned bits.
3. Return pork to pan; cover and cook 18 minutes or until a thermometer registers 155° (slightly pink). Remove pork from pan. Cover with foil, and let stand 10 minutes before slicing. Discard bay leaf.