01 - Place the chopped dark chocolate in a heatproof bowl.
02 - Warm the heavy cream in a small saucepan over medium heat until it begins to simmer, avoiding boiling.
03 - Pour the hot cream over the chocolate and let stand undisturbed for 2 minutes to soften.
04 - Gently whisk until the chocolate fully melts and the mixture is smooth.
05 - Add the butter and vanilla extract; stir until fully blended with a glossy finish.
06 - Cover the bowl with plastic wrap and refrigerate for 2 hours until firm enough to scoop.
07 - Scoop approximately 1 tablespoon of ganache and quickly roll between palms to form balls; place on parchment-lined baking sheet.
08 - Roll each truffle in unsweetened cocoa powder to evenly coat.
09 - Sprinkle a pinch of flaky sea salt atop each truffle.
10 - Keep truffles refrigerated in an airtight container for up to one week; serve at room temperature for optimal texture.