I agree that the stuff you do around the essay is as important as the essay. Separate to the production log I had a mind map, then a time line with whether each stage had been completed and how it had gone and a Gantt chart. Then I had a work log table listing all the things I did, the skills I worked on/gained as a result and an analysis/evaluation. The skills were things like IT skills ie Gantt chart and using Google scholar, communication skills ie discussing things with my tutor, time management/writing/decision making/research skills, I also evaluated all my sources in a table.
A lot what was needed in the production log could then be lifted from my work log and I just expanded on it a little more. Make sure your essay has an intro and conclusion of course and is well structured in between (mine had 3 clear sections - look at how to write research pieces as it's very different from how you write for GCSE! Have references and a bibliography.
Your presentation when you get to it, should give a good overview of the project but more importantly needs to cover skills learned and evaluations of what went well, any difficulties you overcame and what you would do differently if you did it again. This can easily be pulled from the work log if you do one. I got 49 out of 50 for my (Cyber) EPQ.