
What does the expression “(well) kneaded kalach” mean?

It's all about… the recipe. In the old days in Russia, almost every town had its own recipe for kalach – a type of chimney cake. There was a kalach capital – Murom – where the famous kneaded ‘kalachs’ were first baked. Preparing this delicious pastry was not easy. The dough had to be rubbed and kneaded on ice for a long time: the longer it took, the better the kalach turned out. They even said: “не терт, не мят, не будет калач” or “if you don't rub and knead it, you won't have a kalach”.
So, they began to speak of a person who had seen a lot and who was hard to deceive as a “(well) kneaded kalach” – or “an old stager”. For example, in Dmitry Mamin-Sibiryak's novel ‘Privalov's Millions’, lawyer Verevkin instructs his interlocutor: "As a well kneaded kalach, I can give you one golden advice: never pay attention to what they say about people behind their backs.”
An English equivalent would be: “He’s an old salt!”