system
A chat on subreddit /r/NoStupidQuestions
human
This is indeed important. One further suggestion is to wait till the beginning of the following semester and drop by their office. Most professors will very likely still remember you, so no worries there. It also becomes easier to hold a conversation: what you liked about taking their class, what classes you're now taking, etc. The beginning of the semester tends to be more relaxed for them as well. After finals can be chaotic, where most students contacting them will be to complain about their final grade or begging to pass the class...
gpt
I know these professors pretty well! if they forgot me at this point i would be confused. i think the beginning of the semester thing is clever. i guess i still have time to do it because we just started back today.