Detail
lfcarry's professions guide states 'Blizzard has not published the size of the bonus' for Cooking's kill-XP food buff, while Icy Veins (citing the BlizzCon Deep Dive/Twitch reveal) and a beta forum poster both independently give the figure as 5%. The 5% figure appears well corroborated; lfcarry's claim that it was never published appears to be outdated or simply wrong relative to the other two sources.