Well to incite an argument....over 35 years I always used the mixture for engine cuts.....but i will reiterate, low level cuts using either method is fraught with danger and the instructor MUST be proficient and prepared for the unexpected, and, after the student has continuously demonstrated a high proficiency standard of handling such emergencies at altitude. That particular TC in question was one of my previous birds and it was fitted with a contra rotated engine after the original owner suffered an EFATO !