Chop the chocolate into fine pieces and place in a medium bowl then set aside.

Place the cream in a small saucepan and bring to a gentle boil over medium heat (or warm the cream in the microwave). As soon as the cream begins to boil, remove it from the heat and pour it over the chopped chocolate in the bowl.

Let the mixture sit for 30 seconds to melt the chocolate then using an immersion blender, or a whisk, beat the mixture until it is smooth. Stir in the butter.

Pour the mixture into a large ziplock bag, seal it then let it sit at room temperature for about 4 hours until it is thick enough to hold its shape when dropped into a mound.

Line a baking sheet with parchment paper. Clip a corner of the bag off and pipe out small mounds of the chocolate ganache mixture (a little bigger than a teaspoon). If the ganache warms up in your hands while piping and softens too much, place the bag in the fridge for a few minutes.

Place the mounds of piped chocolate in the refrigerator for 10 to 15 minutes to firm them up.

Sift the cocoa powder into a pie plate or shallow dish. Roll each mound of chocolate into a ball then roll them in the cocoa powder to coat.

Store in an airtight container in the refrigerator for up to 2 weeks. Allow them to come to room temperature before serving.