Chop or break the chocolate into small pieces and place in a fairly deep bowl.
Melt the butter and milk together until the butter is melted and it starts to bubble slightly at the edges.
Pour the milk/butter mixture over the chocolate (making sure all of the chocolate bits are covered) and leave for five minutes.
Whisk quickly, until everything comes together and you're left with a thick mixture.
Place in the fridge for a couple of hours to thicken.
Add around 20g of icing sugar to the chocolate mixture and whip/whisk until a thick frosting forms.
Spread all over the cake and top with whatever decoration you fancy.
To make chocolate shavings chill a block of white chocolate and scrape down it with a knife. Decorate with whatever you fancy (or leave as it is). Slice and enjoy!