And in the late Ruth Chew's children's book about two runaways - The Secret Summer, a.k.a. Baked Beans for Breakfast, the kids get the flattest big stone they can find, put it in the fire for a while then take it out, and then (IIRC) they take a slice of bread with a large hole, place it on the stone, crack an egg into the hole, and both the bread and the egg get well-cooked.

Lenona.