The title is a bit over dramatic but, per the title, if you could contribute with one piece of knowledge to a book that every single individual should learn from in order to kickstart a civilization, what would be yours?
My personal choice would be the process of soap making, from scratch.
I would need to do a lot of adjusting for being made over a fire and do a whole lot of temperature, time, pot used, and ingredient amount/type used, but I could provide a cheesy tuna noodle casserole recipe.
Obviously this restarted civilization probably wouldn’t have canned goods, an oven, a stove, a 9x13 glass pan, a clock for timing, and spray oil, so I would have to adjust the recipe to account for all of that before submitting it for that type of book.
Though, what I assume would be the hardest ingredient to come by would definitely be the cream of mushroom and cream of chicken.
Edit:
Looked up what exactly goes into cream of mushroom and it still probably would be the hardest to get due to the diversity of ingredients depending on the recipe.
‘If you have no store-bought cream, hunted and foraged is fine’
There are two types of cream there I was/am not aware of…
I should have been a bit more specific because the ones I use are pretty much just canned condensed soup mix.
Cream of mushrooms and cream of chicken.
What are those?
They’re soups but I have only ever seen them as condensed canned soups. They’re one of those ingredients I’ve used plenty of times but couldn’t really tell you much more about them.
So, its just chicken and mushroom soup. I was picturing specially flavoured cream (as in whisking cream).