01 - In a medium saucepan, whisk together milk, sugar, cocoa powder, cornstarch, and salt until well combined.
02 - Place saucepan over medium heat, whisking continuously, until the mixture thickens and just begins to bubble, approximately 5 to 7 minutes.
03 - Remove from heat and stir in vanilla extract and chopped semi-sweet chocolate until the mixture is smooth and glossy.
04 - Pour pudding into a bowl, cover with plastic wrap pressed directly onto the surface, and refrigerate for at least 1 hour until set and cooled completely.
05 - In a mixing bowl, beat heavy cream with powdered sugar and vanilla extract until soft peaks form.
06 - Layer cookie crumbs, chocolate pudding, and whipped cream in serving glasses. Repeat layers as desired, finishing with whipped cream on top.
07 - Top with shaved chocolate or additional cookie crumbs and serve immediately chilled.