The Origin Recipe is this one from the PWMU Cookbook (buy it here).
Except that it’s not. Well it is, it’s just not the Official Recipe.
And that’s because the creator’s mum can’t leave good enough alone.
You see, when the creator decided that Apple Crumble Day should be a thing, the creator went to their trusty phone, rang their mother, and said “Dearest Mother, how do you make apple crumble?”
To which Mum said “It’s in the PWMU book … except I change bits.” And so, although the Origin Recipe is the one from the PWMU Cookbook, the Official Recipe is this one – which is remarkable similar except it’s got all the optional extras in it.