For the cake, place the flour, bicarbonate, baking powder and cocoa powder together in a large bowl. Add in the eggs, sugar, oil, vanilla and milk and beat together to a smooth batter. Quickly stir in the hot water and place the mixture into 2 greased cake tins and bake at 180`c for 30-35 minutes. Remove from the oven and allow to cool down completely. Meanwhile, make the make the chestnut cream by placing the chestnuts in the milk and soak for an hour. Place into a saucepan with the vanilla and cook for 30 minutes or until soft. Remove of the heat and place just the chestnuts into a processor. Blitz, adding in enough of the milk to create a nice thick cream. Allow to cool then fold into the whipped cream to create the chestnut cream. Use the cream to sandwich the cakes together and roughly ice the outer edge. Chill, then cover the top of the cake with half of the melted chocolate. Place the remaining chocolate into a piping bag and drizzle around the outer edge of the cake so the chocolate drizzles down. Allow to set before decorating the top with cooked chestnuts, berries and sifted icing sugar.