Chop the dark chocolate into small pieces and place it in a heatproof bowl.
In a medium saucepan, heat the heavy cream over medium heat until it starts to simmer. Do not let it boil.
Pour the hot cream over the chopped chocolate and let it sit for about 2 minutes.
Add the butter and vanilla extract, then whisk until the mixture is smooth and glossy.
Cover the bowl with plastic wrap and refrigerate the ganache for about 2 hours or until firm.
Once the ganache is firm, use a cookie scoop or tablespoon to scoop out portions of the ganache.
Roll each scoop between your hands to form a ball.
Roll the truffles in cocoa powder, dip them in melted chocolate, or roll them in chopped nuts or sprinkles for coating.
Place the coated truffles on a parchment-lined baking sheet and refrigerate for another 15-20 minutes to set.
Once set, enjoy your decadent chocolate truffles or gift them in a beautiful box.