1. Make the coconut mixture.Mix the confectioners' sugar, sweetened coconut flakes, and sweetened condensed milk until well combined.
2. Shape the centers. Scoop out about a 1-inch ball of coconut mixture. Roll it round, or flatten and shape it into an elongated Mounds shape, about 2 inches long. Wet your hands if the mixture is too sticky to work with.
3. Freeze. Place the coconut centers on a baking sheet lined with wax paper and freeze for about 30 minutes.
4. Melt the chocolate. Place the dark chocolate melts in a microwave-safe bowl. Microwave in 30-second intervals, stirring between each interval, until melted and smooth, about 1 to 1½ minutes total.
5. Dip. Using a fork, lower one frozen coconut center at a time into the melted chocolate. Spoon chocolate over any uncovered areas. Lift it out and allow the excess chocolate to drip back into the bowl.
6. Transfer. Use a toothpick to gently slide the chocolate-covered candy from the fork onto wax paper.
7. Set the chocolate. Allow the chocolate to set, or place the finished Mounds Bars in the freezer for about 10 minutes to quickly firm the coating.