Acorns are a common material found in The Legend of Zelda: Breath of the Wild. They can be purchased from shop-vendors in Hyrule for 2 Rupees each, and used to make various recipes and elixirs.
An acorn is a seed that grows inside a cup-like shell to protect and nourish it. When it germinates, it becomes an oak tree, one of the most beautiful and majestic trees in the world.
The shell and caps of an acorn can be eaten raw, but the meat has to be treated first to remove bitter tannins that can a) make your mouth feel and taste like felt, b) make you nauseous, and possibly c) constipate you for days.
If you live in an area where oaks grow, you can start looking for acorns around May or earlier. You'll want to know which species of oak you're harvesting, because different oaks bear acorns with different levels of bitter tannins.
Once you've gathered your acorns, rinse them in cool water to remove any loose dirt or hitchhiking bugs. You can then dry them by hand or in a colander set on a rack.
Acorn flour is made by grinding acorns into powder form. It is a great addition to bread, cake, and pancakes for a delicious, nutty flavor and nutritional benefits. It can also be used as a substitute for wheat flour in some recipes.