Preheat the oven to 350 degrees. Then spray the bottom of a 9 inch springform pan with cooking spray.

In a medium mixing bowl, combine the graham style crumbs, melted butter, and 2 tablespoons sugar. Press into the bottom of the prepared pan, making sure to press down firmly. Bake for 10 minutes. And then let it cool.

Melt the chocolate chips and ¼ cup heavy cream together, stirring until smooth. Pour over the crust and spread evenly. Place the pan in the refrigerator to cool completely while preparing the filling.

Then in a medium saucepan, combine the chestnuts, milk, ½ cup sugar, and salt. Bring to a boil over medium heat. As soon as it starts to boil, reduce the temperature and simmer for 15 minutes or until the chestnuts are soft enough to smash easily with the back of a spoon. Take off the heat and add the vanilla.

Put the chestnut mixture into a blender or food processor and process until smooth. Scrape into a bowl, place a piece of plastic wrap directly on the surface of the mixture, and place in the refrigerator until cool.

Whip 3 cups heavy cream with ¼ cup powdered sugar until stiff peaks form. Reserve 1/3 of the mixture to top the pie with. Take a large spoonful of the rest of the whipped cream and stir into the cooled chestnut mixture. Fold in the rest of the whipped cream. Then place the mixture into the cooled pie pan and smooth the top with a spatula. Spoon on the reserved whipped cream and smooth the top. Dust with some cocoa powder and refrigerate for at least 4 hours before serving. Finally remove from the springform pan, dust with more cocoa powder, and serve.