More specifically, grow a tree sapling in a porcelain pot, and feed it 2 dark crystals.
This takes forever. The only reason these things don't cost far, far more than they do is probably that very few people are good enough cooks to put them to use.
Does anyone know the food effects of this item? I'm curious as to what it does, and how much does it sell for? I've seen some on sale, but no price history.