Chaga is a mushroom found on birch trees in northern climates. It's very hard. We collect it ourselves but you can buy it online. We chop it off the tree with an axe making sure to not go too deep into the tree so we don't hurt the tree. We leave what is beneath the surface so the tree and the fungus will continue to grow. I cut it into chunks and simmer it on the stove in a pot of water until it is a nice brown color. Some people grind it up but I like to leave it in chunks so I don't have to strain out the grounds. You don't want to get it too strong. Keep adding water to lighten it up. To me it tastes like coffee. I drink it plain. It is said to have a lot of health benefits.