Doxy Eggs

From UnknowableWiki

Doxy eggs, surprisingly enough, are black eggs laid by Doxys, magical creatures with a poisonous bite. Presumably, their eggs are also poisonous; in the Trio's sixth year, Cormac McLaggen eats a pound of doxy eggs and ends up in the hospital wing, missing the Quidditch trials (HBP11).

When the Weasleys, Hermione, and Harry are cleaning out the drawing room at Number Twelve, Grimmauld Place, they spray a number of Doxys with Doxycide to get rid of an infestation, and when they are finished, their eggs are gathered into a bowl. Fred and George look longingly at the bowl, presumably because they'd like to experiment with the Doxy eggs for their joke shop (OP6).

Doxy eggs are a favorite meal of Bowtruckles, along with fairy eggs and woodlice; because of this, "like Bowtruckles on Doxy eggs" has become a wizarding idiom (DH28).