In a saucepan over low heat, combine the condensed milk, chocolate and butter until it reaches a soft, fudge-like texture. Remove from heat and add the heavy cream.
Line the bottom of a springform pan with parchment paper. Add a layer of cookies and then pour a layer of the fudge mixture over it. Repeat layers until the mold is full, finishing with a layer of the fudge-like mixture. Decorate the top with crushed cookies and chocolate shavings.
Refrigerate for at least 4 hours. Slice and serve.