Whip heavy cream, powdered sugar, vanilla, and cocoa powder together until stiff peaks form.

Spread a thin layer of whipped cream on the bottom of a 9x13-inch dish.

Lay a single layer of Oreo cookies over the cream.

Spread a generous cream layer over cookies; repeat using all cookies and cream, ending with cream.

Sprinkle top with crushed Oreos or chocolate shavings.

Cover and refrigerate at least 4 hours or overnight before serving.