Finely chop the chocolate and add to a microwave-safe bowl. Heat the chocolate in the microwave in 30-second intervals on 50% power, stirring in between, until fully melted.
In a small saucepan, heat the cream until small bubbles form around the edges, or until a food-grade thermometer registers around 125℉ for dark chocolate. Pour the cream over the melted chocolate and allow to sit undisturbed for 1 minute.
Starting in the center, use the rubber spatula to stir in small, rapid circles to start the emulsion of cream and chocolate until it goes from looking like chocolate milk to glossy chocolate frosting. Continue stirring in larger circles until the entire mixture is thick and glossy, 1-2 minutes more.
Tightly press a strip of cling film against the ganache to prevent a skin from forming. Set aside for 2 hours in a cool, dry place.
Add Dutch-processed cocoa powder to a small bowl. Use a teaspoon to scoop out the ganache and roll into a smooth, round ball between your palms. Roll in the cocoa powder and place finished truffles on a sheet of parchment paper. Repeat until all the ganache has been used.
