In this article, we analyse a 2013 press conference hosting the world's first tasting of a laboratory grown hamburger. We explore this as a media event: an exceptional performative moment in which common meanings are mobilised and a connection to a shared centre of reality is offered. We develop our own theoretical contribution - the promotional public - to characterise the affirmative and partial patchwork of carefully selected actors invoked during the burger tasting. Our account draws on three areas of analysis: interview data with the scientists who developed the burger, media analysis of the streamed press conference itself and media analysis of social media during and following the event. We argue that the call to witness an experiment is a form of promotion and that such promotional material also offers an address that invokes a public with its attendant tensions.