Although Meat and Chef sang on the Chef Aid soundtrack it wasn't featured in the Chef Aid 'film', Meat's only part in that is him talking to the children and agreeing to take part in the concert...so on that basis I'd definitely say it's from a fan, but still really very good
( For the record I don't know a lot about South Park
The only reason I remember teh details of Chef Aid is because I was watching it when I got the call to say my first M&G had been cancelled, so it's engraved on my memory!
)