You And Me Quotes (page 50)
... you have not asked me, for instance, what is my favourite flavour of jam, to check that I am indeed Professor Dumbledore, and not an imposter." [...] "For future reference, Harry, it is raspberry ... although of course if I were a Death Eater, I would have been sure to research my own jam-preferences before impersonating myself.
J. K. Rowling