Halloween Mississippi mud pie with blackberries

Method

1. Put the biscuits and melted butter into a food processor and pulse into a sandy rubble. If you don’t have a food processor, put the biscuits in a clean bag and bash into crumbs with a rolling pin, then mix with the butter in a bowl until evenly combined. Press the mixture into the base and sides of the cake tin and put in the fridge to chill.
2. For the filling, heat the oven to 160ºC fan/gas 4. Melt the chocolate and butter together in a heatproof bowl set over a pan of simmering water (making sure the bowl doesn’t touch the water). Meanwhile, use an electric whisk to whisk the eggs and sugar together until thick and creamy – about 5 minutes.
3. Gently stir or fold the cream and melted chocolate mixture into the eggs until just combined (use a large metal spoon and a figure-of-eight motion), then pour this onto the chilled base. Bake in the oven for 50-60 minutes or until just set – a small knife should come out clean when pushed into the centre. As it cools, it will sink in the centre, creating a crater for the ganache and cream to sit in.
4. To make the compote, put the blackberries, sugar and sage in a saucepan over a medium heat. Bring to a simmer and cook for about 5 minutes until the blackberries have broken down a little and released their dark juices but still hold their shape. Remove the sage sprigs and leave to cool (see Make Ahead).
5. To make the chocolate ganache (see Know-how), put all the ingredients in a saucepan and put over a medium heat. Stir regularly until completely combined, smooth and glossy. Leave to cool a little – it should be no cooler than room temperature or it will be difficult to spread and may lose its shine.
6. Once everything has cooled, whip the double cream and vanilla to soft peaks (when you lift out the beaters, the peaks formed will flop over). Add a third of the blackberry compote, then drag a spoon through it once to create a rippled effect. Carefully remove the base from the tin and spread the chocolate ganache over the top, followed by the rippled cream. Finish by spooning the remaining compote over the top of the cream.