Preheat the oven to 170 degrees Celsius. Grease a 20-cm (8-inch) round cake tin and line the bottom with greaseproof paper. (I used a 7-inch round, loose-base cake tin, so besides greasing, I also line the sides and bottom with greaseproof paper.)
Put the chocolate, butter, sugar, milk and coffee together in a large pan. Heat very gently, stirring, until the butter and chocolate have melted, the sugar have dissolved and everything is incorporated and smooth. Remove from the heat and leave it aside to cool for 15 minutes. The mixture will still be a little bit warm.
Transfer the chocolate mixture into a deep bowl and beat in the eggs. Sift the flours and cocoa directly into the mixture and fold the it in. Tip the batter into the prepared tin and bake for about 1 and a 1/2 hours. Leave to cool in the tin for about 30 minutes, then turn out onto a wire rack to cool completely.
To make the icing, put the chocolate in a heatproof bowl. Put the cream into a pot and heat until almost boiling, the sides will be bubbling (with small bubbles), but make sure it does not end up a rolling boil! Pour the hot cream over the chocolate and let stand for 5 minutes. Stir until smooth, then leave to cool and thicken slightly – for about 30 minutes, depending on the weather – before pouring it over the cake. Decorate with chocolate shavings. Or, wait for the ganache to harden, and before serving, dust lightly with cocoa powder.