01 - Place the chopped dark chocolate in a heatproof bowl.
02 - Heat the heavy cream in a small saucepan over medium heat until it just begins to simmer; avoid boiling.
03 - Pour the hot cream over the chopped chocolate and let it sit for 1 minute. Stir gently until the chocolate is melted and smooth.
04 - Add the cubed butter and stir until fully melted and the mixture is glossy.
05 - Cover the bowl with plastic wrap and refrigerate for 1 to 2 hours until firm but scoopable.
06 - Using a teaspoon or melon baller, scoop portions of the chilled mixture and quickly roll into balls between your palms to prevent melting.
07 - Place cocoa powder in a shallow dish and roll each truffle evenly in the powder to coat.
08 - Arrange truffles on a parchment-lined tray and refrigerate for at least 30 minutes before serving.