I was startled to learn (learn? if it's true I learnt, otherwise I merely read) that peanut butter was invented as a subsitute for... can I call it milk butter? As a spread, anyway. Black American biologist... Booker Washington, was it? So butter (of any kind) is long-chain fatty acids with things done to them to make them solidify. Therefore you can do it to peanuts (arachidonic acid)... so just maybe some fruits have fats in them that... oh wait, I've ventured into The Implausible. I don't know.