Chicken Vol-Au-Vent

Every cocktail party, reception, or other catered affair from Ankh-Morpork to Lancre will serve some version of creamed chicken in puff pastry, which nobody likes. This appears to be a universal law of mass catering right across the Multiverse.

It is possible that this appearance of the dish in Discworld was based on Terry's own experience at book launch parties and such.