Finely break the dark chocolate
Pour heavy cream into a saucepan and heat over low heat
Just before it starts boiling, turn off the heat and add the chocolate
Mix well until the chocolate is fully melted
Add the butter and mix until completely combined
Pour the mixture into a flat container and refrigerate for 2–3 hours to set
Remove the set chocolate and cut into bite-sized pieces
Sprinkle cocoa powder over the top