In a medium saucepan, melt the heavy cream and butter over very low heat, stirring constantly, until the mixture just comes to a boil. Remove the saucepan from the heat and immediately add the chocolate and vanilla. Stir until the chocolate melts completely.

Pour the cream into a glass container and refrigerate for about 2 hours. The cream should become semi-firm but not hard, and your fingers should not stick. If it gets hard, let it sit at room temperature to soften.

Line a baking sheet with parchment paper. In 2 separate shallow bowls, add the cocoa and shredded coconut.

Wash your hands with cold water to cool them off. With a spoon, scoop up the chocolate mixture and form it into about 18 balls. Roll the balls in cocoa or coconut, as desired, to coat them well.

Arrange the truffles on the prepared baking sheet. Work quickly to keep the truffles from melting. Chill the truffles in the refrigerator for at least 1 hour to harden.