This is just mad. I read this email and I knew exactly what the answer is. The last time I read the book was before I owned my first samsung touchscreen phone. It's not even that important, how the fuck I remember that it was treacle tart? 
Because every HP fanfic author includes treacle tart being Harry's favorite in their stories 
chaosghost: That's the thing! I did not read HP fanfics much. I only remember reading a bit and all of them were Drarry, then I never read them ever again. I remember exactly reading that in the book, it's just that my memory sometimes is so weirdly specific. 
this reminds me oddly enough of all the spells in HP fanfics that were never in the canon but were just so popular in the fandom that it became widespread
https://tvtropes.org/... oh tvtropes has a list. Of course.
Of course tvtropes has it 