01 - Place chopped chocolate in a heatproof mixing bowl.
02 - In a small saucepan, heat the cream over medium heat until it just begins to simmer. Do not boil.
03 - Pour the hot cream over the chocolate. Let sit for 2 minutes, then gently stir with a whisk or spatula until the chocolate is fully melted and smooth.
04 - Add the butter and vanilla extract. Stir until the mixture is silky and glossy.
05 - Cover the bowl with plastic wrap and refrigerate for 2 hours, or until firm enough to scoop.
06 - Using a teaspoon or small melon baller, scoop out portions of the ganache and roll quickly between your palms to form balls about 1 inch in diameter.
07 - Place the cocoa powder in a shallow bowl. Roll each truffle in cocoa powder until evenly coated.
08 - Store in an airtight container in the refrigerator for up to 1 week. Bring to room temperature before serving.