1. Pour Italian-Mustard Marinade into a shallow dish or large zip-top plastic freezer bag; add chicken breasts. Cover or seal, and chill at least 8 hours or up to 24 hours, turning occasionally.
2. Remove chicken from marinade, discarding marinade. Pat chicken dry, and sprinkle with salt and pepper. Cook chicken in hot olive oil in large skillet over medium heat 6 to 8 minutes on each side or until done.