Add the mashed potatoes to a large bowl. Make sure the mashed potatoes have been mashed with a fork or a potato masher only until no chunks remain and that they appear dry. Over-mashing can cause them to become gluey and too fluid for this recipe, so it's a good idea to squeeze the mashed potatoes with a piece of kitchen paper (paper towel) to absorb any excess moisture.

Add the peppermint extract to the potatoes and give them a quick stir to combine. Add the powdered sugar to the bowl one cup at a time, stirring well with a wooden spoon after each addition. Because the water content in the potatoes will vary, add just enough powdered sugar to form a soft dough (4-6 cups should be enough). Once the mixture forms a soft dough, pour the contents of the bowl onto a clean work surface and work the dough with your hands, adding a sprinkling of powdered sugar as needed until it forms a mixture similar in appearance to play-dough (in other words, it's not too sticky to handle but it's still soft).

Take pieces of the dough in your hands and roll them into balls about 1 to 1.5 inches in diameter. Set the balls on a parchment-lined baking tray and stick them in the freezer to firm up for about 10 minutes.

While the balls are in the freezer, chop the dark chocolate and add it to a microwave safe bowl. Microwave the chocolate at 50% power, stirring after every 30 second increment until it's completely melted. The other way to melt the chocolate is in a double boiler (in a heat-safe bowl over gently simmering water on the stove), which is obviously the way my great grandmother used to do it!

Pour the shredded coconut onto a large plate and remove the balls from the freezer. Dip each ball into the melted chocolate until it's completely coated and then roll it in the shredded coconut so the coconut sticks to the surface of the melted chocolate.  Place the truffles back onto the parchment-lined baking sheet. Once they're all dipped in chocolate and rolled in the coconut flakes stick the baking sheet in the freezer again just until the chocolate firms up, and serve!