Faerie Changelings...

A small cottage in Trefeglwys was the place
of much trouble between the husband and wife.
They were constantly arguing about their twins,
who the mother was convinced had been
swapped for faerie changelings.
A local Wizard was called in to  advise them.
An eggshell was to be boiled and made into a
stew which then had to given to the farm workers
for dinner.
If the twins said or did anything unusual then it
was certain that they were faerie changelings, and
then should be thrown into the Llyn Ebyr Lake.
As soon as the shell began to boil they started to
chant
“Acorns before Oak I saw,
An Egg before a Hen,
But never one hen’s egg stew
Enough for harvest men.

With this the mother took them straight to the lake
and threw them in.
A group of faeries immediately appeared to
save them from drowning.
They handed back the stolen children and then
disappeared back into the hills.

Faeries and Folklore of the British Isles