In a small mixing bowl, whisk together the cornstarch and powdered sugar. Place half the sugar mixture into a sifter and sprinkle it over a sheet pan, making sure to coat the entire pan.
Grease a large microwave-safe bowl with the butter, then add in the marshmallows. Microwave on high for 1-2 minutes, making sure to stir every 30 seconds until they are melted.
Pour the marshmallows onto the prepared sheet pan. Sprinkle the top with half of the remaining sugar mixture. Rub your hands with the sugar mixture and press the marshmallow out flat in an even layer about ΒΌ inch thick. Anywhere that becomes sticky, just sprinkle it with the sugar mixture. Allow the marshmallow to set for 30 minutes.
Dip your circle cookie cutter into the sugar mixture and cut out as many circles from the marshmallows as you can fit. Using a pastry brush, dust the sugar mixture off the marshmallows and set them to the side.
Melt your chocolate according to the directions on the packaging. Drizzle the tops of the marshmallow circles with the chocolate. Sprinkle the crushed candy cane over the top of the chocolate. Allow the chocolate to set for 20 minutes. Break the chocolate from the sides of the marshmallows.
Place a marshmallow into your favorite cup of hot chocolate and enjoy!
