Put the butter in a microwave-proof bowl and microwave for 30 secs, until melted.

Transfer the butter in a large bowl and add the chopped chocolate. Mix until the chocolate has melted and you have a smooth mixture.

Mix in the sugar slowly, alternating it with the milk.

Mix all the ingredients until the frosting reaches a smooth rich consistency.

Use it straight away, or refrigerate for 15 min if you want a more solid texture.

Store in an airtight container for up to 4 days in the fridge.