Dwarven bread

In real life: A supposedly edible item that nobody actually tries to eat.

Mainly used a synonym for any failed cookery experiment but also for wrapped food in bottoms of bags that have been there since forever.

Originally from the Disk World series by Sir Terry Pratchett. Bread baked from the finest stone-ground grit. The point of having it is to keep you going on the idea: "I'm not *that* hungry."

The smoke alarm in the kitchen sounds. "Looks like you made dwarven bread. I'll order pizza."

Quote from 'Witches abroad':
The dwarf bread was brought out for inspection. But it was miraculous, the dwarf bread. No one ever went hungry when they had some dwarf bread to avoid. You only had to look at it for a moment, and instantly you could think of dozens of things you'd rather eat. You're boots, for example. Mountains. Raw sheep. Your own foot.