01 - Place the chopped dark chocolate in a heatproof bowl.
02 - Warm heavy cream in a small saucepan over medium heat until it just begins to simmer, then remove from heat.
03 - Pour the hot cream over the chopped chocolate and allow it to sit for 2 minutes.
04 - Gently stir the mixture until the chocolate is completely melted and smooth.
05 - Stir in the unsalted butter and vanilla extract until fully combined and glossy.
06 - Cover and refrigerate the mixture for at least 2 hours, until firm enough to scoop.
07 - Scoop small portions using a melon baller or teaspoon, then roll into balls between your palms.
08 - Roll each truffle in sifted cocoa powder to coat evenly.
09 - Place coated truffles on a parchment-lined tray, sprinkle with flaky sea salt, and store in an airtight container in the refrigerator until ready to serve. Allow truffles to sit at room temperature for 10 minutes before enjoying.