Preheat the oven to 150C/300F/Gas 2. Grease the insides of a deep 20cm (8in) round cake tin, or loose-bottomed 20cm (8in) cake tin, with olive oil and line the bottom of the tin with greaseproof paper. If you are using a loose-bottomed tin, double-line it with greaseproof paper (line the base, the sides, then line the base again to seal the lining), to prevent the mixture leaking out.

Sift the flour, cocoa powder and bicarbonate of soda into a large bowl, then add the sugar, ground almonds and salt. Make three holes in the dry mixture with a spoon. Put the vanilla in one hole, the vinegar in the second, and the oil into the third. Pour in the prune juice and mix well. Bubbles will start to rise to the surface. Pour the batter into the prepared cake tin and bake for 45 minutes to one hour, or until a skewer inserted into the centre comes out clean. Remove the cake from the tin and leave it to cool on a wire rack.

To make the ganache icing, blitz the chocolate into crumbs in a food processor. Place the crumbs in a heat-proof glass bowl. Heat the milk to boiling point in a heavy-based saucepan, then pour the milk over the chocolate. Gently mix the chocolate with the milk, working from the centre of the bowl outwards with a rubber spatula, until you have a smooth and glossy emulsion. Let it cool to room temperature, then spread it on top of the cooled cake.

NB this cake usually takes about 1 hour 15 mins to cook! Keep testing it, but don’t take it out of the oven to do so, otherwise it may sink.