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 peppermint extract.
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 and white chocolate melting wafers in 2 separate bowls.
Microwave each bowl for 30 seconds at a time, stirring between each interval, until smooth and melted through.
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.
Coat half the truffles with dark chocolate and half of them with white chocolate.
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.
Chop Andes Mints into small pieces. Place a few pieces on top of each truffle to decorate.