eggs in moonshine

Probably from the name of a dish, referred to in 16th- and 17th-century English cookbooks, made of egg yolks lightly poached in sweetened rosewater. See also moonshine, culinary sense (US).

eggs in moonshine (uncountable)

1. A fanciful notion; an unrealistic or ludicrous concept.
   • 1593, Gabriel Harvey, Pierce's Supererogation, or, A New Praise of the Old Ass‎:

     You may discourse of Hermes' ascending spirit, of Orpheus' enchanting harp, of Homer's divine fury, of Tyrtaeus' enraging trumpet, of Pericles' bouncing thunderclaps, of Plato's enthusiastical ravishment, and I wot not what marvellous eggs in moonshine: but a fly for all your flying speculations when one good-fellow with his odd jests, or one mad knave with his awk hibber-gibber, is able to put down twenty of your smuggest artificial men, that simper it so nicely and coyly in their curious points.

   • 1951, C. S. Lewis, Prince Caspian, Collins, 1998, Chapter 7,

     […] your Majesty knows I think the Horn—and that bit of broken stone over there—and your great King Peter—and your Lion Aslan—are all eggs in moonshine.

• pie in the sky