Place chopped dark chocolate pieces in a small heat-proof bowl.
Simmer the cream in a small saucepan, heating just until it comes to a boil.
Pour the hot cream over the chopped chocolate.
Put a large plate or lid over the bowl to trap the heat. This will melt the chocolate.
Once chocolate is melted (about 5-7 minutes) add the rum.
Whisk chocolate/cream mixture until it turns into a glossy chocolate ganache. If needed, microwave the mixture for a few seconds at a time and stir until smooth if some of the chocolate has not melted all the way.
Place the ganache in the refrigerator or freezer for about 2 hours to firm up.
Scoop tablespoons of the firm chocolate ganache and roll it between your hands to form round balls.
Place the formed truffles onto a sheet pan lined with parchment paper. Put the truffle balls back into the refrigerator to chill for at least 30 minutes longer.
Meanwhile, melt the dark chocolate melting wafers in a bowl. Microwave for 30 seconds at a time, stirring between each interval, until smooth and melted through.
Roll some of your chilled truffles in cocoa powder to coat.
To coat in a hard chocolate coating, set a truffle onto a fork (do not stab with the fork). Dip one truffle at a time into the melted chocolate, coating on all sides, then lifting from the chocolate.
Tap the fork gently to shake off excess chocolate and then set on a sheet of parchment paper.
Allow chocolate to set.
Transfer the remaining melted chocolate into a small ziploc bag or piping bag. Snip off the corner of the bag and drizzle melted chocolate over the tops of the set truffles.
Sprinkle with gold sprinkles.