Pour the heavy cream into a saucepan and bring to a boil.

Break the chocolate into small pieces and melt it in a double boiler with 1 tablespoon of water.

Once the chocolate is melted, remove from heat and whisk in the cream and butter until the mixture is smooth and even.

Let cool, cover, and refrigerate for 6 hours or freeze for 2 hours.

Take out the ganache and put the cocoa powder in a shallow dish.

Scoop out the slightly firm ganache with a small spoon, shape into small balls, and roll them in the cocoa powder. Chill until ready to serve.