Does anybody know how to make Creme de Menthe?

I just spent 20-some minutes looking though a couple dozen videos and NONE show you how to make the actual drink! All they show is how to make the green stuff!!
If you're tending bar and someone asks you to make them a Creme de Menthe, what do you put into it?

Does anybody know how to make Creme de Menthe?
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