The approximate timeframe for the addition of vanilla is unknown (roughly the 1980s) but it is credited to a friend of the brewery named Guy Derdelinckx. According to Van Roy, “one day Guy suggested I try a new aperitif, whereupon he reached into the refrigerator and took out a bottle of raspberry lambic containing a pod of vanilla. When I tasted it I was pleasantly surprised because it turned out that the vanilla flavor really offset the beer’s excessive tartness. Guy had had a stroke of genius and thanks to him I was able to naturally soften the somewhat rough character of certain vintages”.<ref name=GrummelslinkseJune> Van Roy, Jean-Pierre. (2016a). Grummelinkse – June 2016. Musée Bruxellois de la Gueuze. Brussels, BE.</ref> From that point forward, the brewery used a small amount of vanilla extract in each batch.
In addition to using vanilla to cut down on the acidity, at one point a customer of the brewery named Paul Coorevits came up with a drink called the ‘Brussels Kir’ which was “Cantillon raspberry lambic in a flute glass mixed with a bit of strawberry liqueur” that not only would “bring down the tartness, it also enhanced the beer’s colour.<ref name=GrummelslinkseJune> Van Roy, Jean-Pierre. (2016a). Grummelinkse – June 2016. Musée Bruxellois de la Gueuze. Brussels, BE.</ref>