In a large bowl, put in the chopped chocolate and butter at room temperature
In a saucepan, heat the cream, just until you see bubbles.
Take off the heat, and pour it over the chocolate and butter
Using a spatula or a spoon, mix it well, until smooth and glossy.
If you still see chunks of chocolate at this stage, that haven't melted, put the bowl in the microwave for 30 seconds, or melt it completely over a double boiler
Add the peppermint extract and mix well
Refrigerate for atleast 2 hours, until it is firm enough to form balls