I only know the STAR method (or technique) as something that is used during interviews when being asked things like: "Tell me about a time when you xxx". In this context STAR stands for:
S = situation (describe the situation and set the scene)
T = task (describe the reason why you were doing something or the purpose of your task)
A = action (vividly explain what you were doing step by step)
R = result (explain what results you have achieved and also what consequences this has had)
I am sure one could also write an essay using the STAR method. Hence, you would first describe the situation of you making a mistake (who, what, where, when) followed by the reason why you were doing this task as well as how and why the mistake happened. Then you would vividly describe the action (first of all, moreover, therefore, furthermore, consequently, finally, etc.). Finally, you talk about the result. Ideally, you would say what you have learned from making this mistakes and how it has made you better or prepared you for the future. Besides, the second part of the question ("Mention how you worked under pressure") is something you need to work into your story. But that is not difficult, because realizing that you just made a mistake has certainly put you under a lot of pressure. So, invent something along the lines of "This was the moment when I realized that I need to remain calm, clear my head, and think straight. I was at first surprised how well I managed the situation under so much pressure, but I suppose I became aware of how important it was to fix the issue and find a solution". Just a suggestion ......
