Tracking "On The Job" training?

Content

I need to create a Learning Plan that incorporates "On the Job" training. Usually this means that their supervisor went over a piece of equipment or procedure with them. I need this to be a required part of their Learning Plan, but I am unsure how to go about setting this up. I cant set it up as an enrollment, because no set schedule exists (it is done whenever they have free time).

The only thing I can think of is to create an assessment to confirm that they indeed went over the content. If they pass the assessment we can assume that their supervisor went over the content with them. But this doesn't track when the training actually took place, just when they took the assessment.