The author, who left Germany before the war and later returned to live in East Germany, based his novel on the massacre of more than a dozen residents of Charlottenberg, on a street where a storm trooper had earlier been killed (one of the greatest of all World War Two novels, Harry Mulisch's The Assault, also concerns Nazi reprisals on citizens unlucky enough to be in the vicinity of Resistance killings, but I digress).
He baked the manuscript into two cakes and, dressed in skiing clothes to give the impression he was going on holiday, he smuggled it past the SS guards.
"Well, you know what women are, don't you? I told my wife I was only going away for three days, but she would go and bake me two whopping big cakes," Petersen told the customs guards. "It'll take me a week to eat one. Just look at the size of them."
Ha, dem crazy dames, amiright?
Probably the closest historical analogy is the story of The Gulag Archipelago, which Solzhenitsyn baked inside of 400 pieces of rugelach, which he then ate in a single sitting and subsequently regurgitated in Zurich, where he reassembled the manuscript with the aid of his editor.