The magician shows a small square of silk and stuffs it into one fist. The fist is opened to show an egg, but spectators notice that there is a hole in the egg through which the magician obviously stuffed the silk. The magician peels off the hole, showing that it is actually a sticker and cracks the egg into a bowl to show that it is real.
The trick is repeated until enough eggs have been broken to make pancakes, after which the magician switches to a milk bottle or flour production routine to obtain additional ingredients.
This one is all about fakes.
The silk is reversible. It appears to be a normal silk on one side, but if balled up and turned inside out, it appears to be an egg. The hole in the egg is likewise a fake -- a sticker, just as it appears. The sound of the fake egg breaking is made by the magician crushing a real egg underfoot, out of the audience's sight. And finally, the contents of the broken egg are fake, constructed from grocery-store "egg products" and carefully hidden in the magician's sleeve until such time as they need to be poured out from "inside" the "egg."
The famous "Flag to Ostrich Egg" routine works in exactly the same way, as does "Lint Square to Humingbird Egg" (a close-up effect).