Chop 8 oz dark chocolate finely and place in a heatproof bowl
Heat 1/2 cup heavy cream in a saucepan until just simmering
Pour the hot cream over the chocolate
Let sit for 1 minute
Stir until smooth and fully combined
Add 1 tablespoon butter and 1/2 teaspoon vanilla extract, if desired
Mix until glossy
Cover and refrigerate for 1 to 2 hours, until firm enough to scoop
Scoop small portions and roll into balls
Roll the truffles in cocoa powder, powdered sugar, chopped nuts, or shredded coconut
Refrigerate until ready to serve