I have peppermint/mint growing in my garden backyard. I want to make mint candies for children and in one of the YouTube videos they have menthol crystal as one of the ingredients for mint candies so I am wondering how to make Menthol Crystal from fresh mint leaves ?
Every recipe I’ve seen asks for mint extract, which is mint that has had the flavors removed by steam distillation. This is not very difficult to do if you purchase some glass distillation equipment from a science supply company. There would be no need to further process it to pure menthol and crystallize. There are plenty of videos on YouTube which demonstrate essential oil distillation. Making crystalline menthol would likely involve solvent extraction, and could produce a toxic finished product if the menthol were not sufficiently dried.
There was a really good answer to the version of the question you asked last week.
You don’t, unless you have extensive chemical equipment and knowledge (and in that case, you probably wouldn’t be asking here).
Pure menthol is produced either synthetically or from the essential oil of peppermint in a rather complex process. Details for example in the link above.
As a cook and gardener, you would have to get the essential oil before even attempting that and this is already pretty complicated. You need a lot (a huge lot-lot) of mint for just a few drops of oil and a complex extraction process as well.
So you better find another use for your garden mint.