I think the best is borts, Mongolian dried meat. They get a whole animal and cut the meat into very thin strips, then air it out for a year, until the meat is so dry that it crumbles into powder. They took the powder and put it in a bag and took it with them when on a campaign. All you had to do was add a couple of spoons to hot water, stir it, and drink it on down. Those two spoons would completely fill you up. Soldiers on campaign need a lot of calories every day, but a bag of borts would last them for many months, and it basically never spoiled