Preheat oven to 350.

Add the wafer cookies (or graham crackers) and sugar to a food processor and process until just crumbs. While the food processor is running add the melted butter and process until well combined. Add to a deep dish 9.5 inch pie pan. Starting with the sides, press into shape. Press the crust very well until even and compacted.

Bake at 350 for 10 minutes.

Remove from oven and allow to cool.

Add the chocolate to a small bowl.

Heat the stout and cream together until very hot and just starting to steam (microwave or stove top will both work fine). Pour hot liquid over the chocolate and stir until the chocolate has melted and is well combined with the stout and cream. Pour in an even layer in the bottom of the crust. Refrigerate until set, about 30 minutes.

Add the chocolate to a small bowl. Heat the stout until very hot and just starting to steam (microwave or stove top will both work fine). Pour hot beer over the chocolate and stir until the chocolate has melted and is well combined with the stout. Allow to cool to room temperate. In the bowl of a stand mixer add the cream and powdered sugar, building up speed beat on high until medium peaks form. While the mixer is running slowly drizzle the chocolate into the mixer. Once all the chocolate has been added, stop the mixer and remove the bowl. Using a wooden spoon or spatula gently fold until the chocolate and cream have been well combined.

Add the mousse to the pie crust in an even layer, refrigerate until set, about 3 hours.

In the bowl of a stand mixer beat the mascarpone and powdered sugar until well combined. Add the heavy cream and vanilla, beat on high until medium peaks form. Spread in an even layer on top of the pie. Chill until ready to serve.