In a large mixing bowl, whip the heavy cream, powdered sugar, and vanilla extract together until stiff peaks form. This should take about 3-5 minutes using an electric mixer on medium speed.
On a serving platter, spread a thin layer of the whipped cream mixture to create a base.
Place a layer of chocolate wafer cookies on top of the whipped cream, covering the entire surface.
Drizzle a layer of chocolate syrup over the cookies, then spread another layer of the whipped cream mixture on top.
Repeat the layering process (cookies, syrup, whipped cream) until all ingredients are used, finishing with a layer of whipped cream on top.
Cover the cake with plastic wrap and refrigerate for at least 4 hours, or overnight for best results. This allows the cookies to soften and the flavors to meld.
Before serving, garnish the top with grated chocolate or chocolate shavings.