Line a baking sheet with waxed paper. Set aside.

In a medium sized bowl, use a hand mixer to combine the powdered sugar, sweetened condensed milk, and peppermint extract. A thick dough will form.

Sprinkle powdered sugar on a clean work surface and rolling pin. Roll out the dough to a ¼ inch thickness. Use a small biscuit cutter or something else small and circular, like a shot glass, to cut circles out of the dough until all the dough is used. Transfer the dough circles to the prepared baking sheet.

Place the baking sheet in the refrigerator for 30 minutes to an hour to chill.

After the dough chills, melt the chocolate. Place the chocolate and oil in a microwave safe bowl. Heat for 2 to 3 minutes, stirring every 15 to 20 seconds, until the chocolate is smooth and completely melted.

Use a fork to dip the dough circles into the melted chocolate. Shake off any excess chocolate, and transfer the patties back to the baking sheet. 

Transfer the peppermint patties back to the refrigerator to chill for another 30 minutes to an hour.. Store the peppermint patties in the refrigerator until ready to serve. They’ll stay good for about 4 to 5 days.