Many years ago when I was teaching Biology and helping students come to terms with dichotomous keys as mechanisms to determine identities, we developed one (on the basis of presence/absence of egg/sugar/milk/etc, as well as cooking styles, to differentiate between a wide variety of edible (and not so edible) things that all included flour as an ingredient.

Mercifully, in the context of this thread, we stuck to what was observed in Victoria (Oz) and didn't have to cope with transatlantic definitions, let alone UK intracounty 'nonsense'.

Nun's farts, indeed. Why hadn't I ever come across one? I feel deprived.

Cheers, Rowan