No from what I remember you can mention how it went wrong and what you would change next time, I handed up my assignments in october so I can't remember the heading but I think you're supposed to do it under a different heading not evaluation, could be wrong I'd check with your home ec teacher if you can
That sample is terrible!! If you go through your implemetation as if everything is perfect and then introduce a huge problem in the evaluation i.e. you are contradicting yourself then yes you might not be awarded full marks. Evaluation points should be measurable e.g. I would boil the pasta for 12 minutes instead of 15 as I felt the pasta was too soft and would be better with an al dente texture.
Again make sure this isn't contradicting what you have previously said in your description of the dish.
Be honest in the write up. Its easier. The point is to see if YOU can see where you went wrong and know how you fix it or how it should have gone. I messed one of my cooking practicals up compleatly but that actually gave me more to write about. You can describe how it should have been vs how it was and why that happened. A perfect dish is boring and can sound like a lie if everything goes well.