Place the chopped chocolate in a heatproof bowl set aside while heating the cream.

In a small saucepan, heat the cream over medium heat until it just begins to simmer. Do not boil.

Pour the hot cream over the chocolate. Let it sit for 2 minutes, then gently stir until the chocolate is fully melted and smooth.

Add the butter and vanilla extract, stirring until completely incorporated and glossy.

Allow the ganache to cool to room temperature, then cover and refrigerate for at least 2 hours, or until firm enough to scoop.

Line a baking sheet with parchment paper. Using a teaspoon or melon baller, scoop out small portions of ganache and roll into balls with your hands.

Place the cocoa powder in a shallow dish. Roll each truffle in cocoa powder to coat evenly.

Store the truffles in an airtight container in the refrigerator. Bring to room temperature before serving for best texture.