Line a 23cm wide by 4cm deep pie tin with foil
To make the biscuit base melt the butter in a pan and whizz up the Oreos in a food processor or put them in a bowl and bash them with a rolling pin until they are crumbs
Add the melted butter into the Oreo crumbs and stir well. Then pour them into the lined tin and use the back of a spoon to smooth them around the base and sides to create the pie crust. Chill the crust for 30 minutes in the fridge
Pre-heat your oven to 180C/160C Fan/350F/Gas Mark 4
To make the filling melt the dark chocolate and the butter in a glass bowl over a pan of simmering water. Do not let the bowl touch the water. Set the melted chocolate and butter mixture aside
Whisk the eggs with the light brown sugar until frothy
Add the chocolate mixture slowly to the egg mixture, whisking constantly. Then add the cocoa powder and the double cream and whisk in
Slowly pour the filling into the chilled pie crust. Bake the pie for 35 minutes
Leave the pie to cool in the tin, it will come out of the oven quite puffed up and will settle and sink down as it cools
Once completely cool remove the pie from the tin and remove the foil, place it on a serving dish or cake stand
Whip up the double cream with the icing sugar and vanilla extract, either with an electric whisk or by hand, until stiff peaks form. Pipe or spread it on top of the pie. Finish with chocolate shavings or grated chocolate
Keep in the fridge, the pie will last for 3 days