Good evening.
Well, if your audience is familiar with your first essay, you absolutely can refer to it in your second piece. If, on the other hand, the audience has had no exposure to the first piece it would make your references to it rather cloudy and lose some of your audience, and in that case you should include at least the most important topics of your first essay in a brief overview so that your audience will be somewhat familiar with the material.
I hope this helps!
Regards,
Gloria
Moderator, EssayForum.com
Gloria, EssayForum.com