I vaguely recall Warninks Advocaat being on TV at Christmas Time when I was a kid & I decided to try it for the first time in some seasonal cocktails. My version of the Fluffy Duck keeps all the ingredients & ratios the same except I substituted Fever Tree Blood Orange Soda which not only gives the drink an added orange zing but a lovely pale orange layer above the heavier Advocaat mix. Try it! Since mine could be considered a riff on the original I called it the Ducky Fluff :)
Many thanks, Louise. I've added a quote from the newspaper above. This suggests Fluffy Duch was served straight-up in a cocktail glass. However, the other vintage quote I've found suggests a long cocktail with soda. I wonder which came first - the fluffy duck or the egg? Be interesting to see what else turns up. Thanks again.