1. Mix the heavy cream and the coffee granules in a small saucepan. Bring to a boil and remove from heat.
2. Place the chocolate into a tall, narrow container and pour the hot cream over it. Allow it to sit for a few seconds, then blend with an immersion blender until you have a smooth consistency.
3. Pour the cream over the base and allow it to cool to room temperature. Transfer the pan to the freezer and freeze for at least an hour, until ready to serve. Remove from freezer and cut into rectangles or squares in the size of your choice.
4. These squares last for two months in the freezer.