Butter the base of 22cm loose-bottomed round cake tin and line with baking parchment. Heat the oven to 160C/140C fan/gas 3. Break the chocolate into a saucepan, then add the butter and coffee. Heat until the chocolate and butter are just melted, but do not allow to boil. Remove from the heat and leave to cool slightly.

Meanwhile, mix the flour, baking powder, bicarb, sugars and cocoa powder together in a bowl until no lumps remain in the mixture. In another bowl or jug, mix together the eggs and buttermilk. Stir the melted chocolate mixture and the egg mixture into the flour mixture to make a smooth batter.

Pour the batter into the prepared tin and bake for 50 mins-1 hr 30 mins, or until a skewer inserted into the middle of the cake comes out clean. If the top of the cake starts to brown too quickly, cover with foil or a sheet of baking parchment. Don't worry if the top starts to crack slightly, as the ganache will cover this. Leave to cool slightly in the tin (it will sink down a little), then turn out onto a wire rack and leave to cool completely. Remove the tin and baking parchment.

Cut the cooled cake into three layers through the equator, using a sharp knife or cake wire. For the ganache, break up the chocolate into a heatproof bowl. Warm the cream and sugar in a pan over a medium heat until steaming, then pour over the chocolate. Let stand for a minute, then stir until smooth.

Put one of the cake layers on a cake board or stand, spread some of the ganache over the top, and repeat with the remaining cake layers. Spread the remaining ganache all over the top and sides of the cake, then decorate with grated chocolate or chocolate shavings. Will keep chilled for up to four days. This recipe has been provided by Apetit Online and not been re-tested by us.