Recipe for Chocolate Buttercream (Discovered with Chocolatecakezilla)

Okay so I know having no measurements isn't particularly helpful so I'll try and estimate but it really depends on the size of your cake-this is for a 12" VERY deep chocolate cake, filling and icing. It's also a lot down to personal taste and I did have some buttercream left over.

 approx. 350g Unsalted Butter (I'm vegetarian and if you are too check that it's veggie butter :) )
 approx. 500g icing sugar
 approx. 150g dark chocolate (I like to use bourneville)
 approx. 100g cocoa powder (Again-I like the bourneville one)
 approx. 50g drinking chocolate (I used cadburys)
 approx. 4-5tbsp nutella (Nutella gives it an edge but if nut allergy replace with normal chocolate spread.)
 You may also need 2-3 tbsp milk.

1. Melt the chocolate either in a microwave or over a pan of boiling water, stir and leave to cool.
2. Cream the butter.
3. Add all of the icing sugar gradually, tasting as you go along-if it tastes too sweet don't add it all, if not sweet enough, add more.
4. Add the cooled chocolate, cocoa powder, drinking chocolate and nutella (Or spread) and whisk until combined.
5. Taste and use your judgement. If it's too sweet add more cocoa powder/drinking chocolate/milk. If it's not chocolatey enough add more cocoa powder/drinking chocolate. If not runny enough add more milk/nutella (Or spread). If too runny add more cocoa powder/icing sugar. If not sweet enough add more icing sugar.
6. When you're happy with the taste and texture spread onto your cake! (Or eat with a teaspoon.)