This recipe makes one 20cm (8 inch) pie. Double the recipe to make a 28cm (11 inch).
Cut chocolate into small cubes.
Add cream to a small pot and add chocolate. Over medium heat cook until chocolate has completely melted, about 5 minutes. Use a whisk to mix constantly.
Remove from heat and let cool to room temperature. Move to the fridge and leave to rest overnight.
After the mixture has chilled whip it using an electric mixer like you would whip cream. Transfer to a piping bag with the desired nozzle. If you whipped the chocolate cream before making the pie, leave it in the fridge to wait for decoration.
Use a food processor to finely grind the cookies.
Meld butter and chocolate in a small bowl over a pot with simmering water. Add to the ground cookies and mix well.
Transfer the cookie mixture to the pie tin and press to the bottom and the sides to form a firm pie crust.
Leave to set for at least two hours in the fridge or 30 minutes in the freezer.
Add cooked chestnuts, sugar and cream to a small pot and bring to a boil. Then immediately lower the heat and let simmer for 15 minutes.
Transfer to a blender and mix until smooth.
Pour onto the chilled cookie base and let cool for at least 3 hours.
Pipe the chocolate cream around the edge of the pie.
Store the pie in the fridge. Leave it at room temperature for 30 minutes before serving.