unboil

un- +‎ boil

unboil (third-person singular simple present unboils, present participle unboiling, simple past and past participle unboiled)

1. (transitive) To reverse the process of boiling.
   • 2012, Frederick Bettelheim, ‎William Brown, ‎Mary Campbell, Introduction to Organic and Biochemistry (page 359)

     These proteins help a partially heat-denatured protein to regain its native secondary, tertiary, and quaternary structures. Some denaturation, however, is irreversible. We cannot unboil a hard-boiled egg, for example.

• Blouin