Add the powdered sugar, sweetened condensed milk and peppermint extract to a mixing bowl and mix into a thick dough. If it seems like it won't come together properly then get in there with your hands and form it into a ball of dough.
Break off pieces of the dough and form them into balls and place them evenly onto a parchment lined baking tray. If the dough is sticky, then dust extra powdered sugar on your hands and on top of the dough to prevent stickiness.
Cut out a small square of parchment paper and place the parchment paper on top of each ball and then press down gently with the base of a glass to flatten it. The parchment paper stops the bottom of the glass from sticking.
Place the whole tray into the freezer for around an hour so that your peppermint patties can set very firmly. They should be super hard to the touch before you dip them into the chocolate.
Break up your chocolate and place it into a microwave safe bowl along with the coconut oil and microwave in 30-second intervals, bringing it out to stir every 30-seconds until the chocolate is completely smooth and melted.
Dip the peppermint patties into the melted chocolate using two teaspoons to dunk it in the chocolate and then lift it out again, placing it back onto the parchment lined baking tray.
Sprinkle crushed candy canes on top (optional) and place them into the fridge to set.