To make the chocolate icing: use an electric beater / freestanding mixer to soften the butter. Sift in the icing sugar and cocoa. Mix until the butter and icing sugar are combined (the mixture will be very stiff.) Warm the milk in the microwave, then add gradually until you have a smooth, spreadable icing.
Break the dark chocolate into pieces and place in a bowl. Heat the cream gently just until boiling point, then pour over the chocolate. Add the butter. Leave to stand for a minute, then whisk until smooth. (Ganache recipe used with permission from Bibby's Kitchen at Thirty Six.)
Place one of the chocolate cakes on a plate. Spread half a tin of caramel over the top. Place the second chocolate cake on top of that, then spread the remaining caramel on top of it. Place the third chocolate cake on the top.
Carefully spread the chocolate icing over the top and sides of the cake. I prefer a slightly rough finish but you can choose how smooth or rough you would like it. Set the cake aside to allow the icing to set.
Pour the chocolate ganache in the centre of the cake, gently coaxing it over the sides to make gorgeous chocolatey drips.
Drop chocolate malt balls over the top with reckless abandon, the more the better! Finish the cake off with a sprinkling of edible glitter, this is completely optional though.