If you want to stump someone while playing hangman, one of these two words ought to do it.
Ersatz. The unlikely combination of letters, the fun sound of this word and its definition make it a great addition to anyone’s vocabulary. Ersatz is an adjective meaning “being a usually artificial and inferior substitute or imitation”. “Ersatz eggs” would be a great way to describe powdered vs. real eggs. (“Ersatz” may also be the sound you make while trying to spit out powdered eggs.)
Erstwhile, meanwhile, can be used as an adverb (meaning “formerly) or an adjective (meaning “former”). The erstwhile chef was unsuccessful at passing off powdered eggs to her clientele.