Hard-tack n. : A name given by soldiers and sailors to a kind of hard biscuit or sea bread.

Example:
How many minutes should you cook the hard tack candy at 300 degrees?

Taxonomy
Operation Hardtack, pilot bread, cracker, food, biscuit, bake, free encyclopedia, the American Civil War, commercially, Alaska, sea biscuit, sea voyages, long sea, water crackers, Pilot, Alaskans, Interbake Foods, South Korea.

Defination from the web:
hard tack) is a simple type of cracker or biscuit, made from flour, water, and salt. ... Baked hard, it would keep for years as long as it was kept dry. ... also referred to as a staple food of Chinese hard-labor workers in Inner Mongolia during the Cultural Revolution ...