In a mixing bowl, combine the powdered sugar and sweetened condensed milk. Mix until a soft dough forms.
Add the peppermint extract to the dough and mix well to combine.
Taking small amounts of the mixture, form it into round patties and place them on a baking sheet lined with parchment paper.
Refrigerate the patties for about 20 minutes until they are firm.
In a small saucepan over low heat, melt the chocolate chips and vegetable oil together, stirring constantly until smooth.
Remove the patties from the refrigerator. Dip each patty into the melted chocolate, ensuring it is fully coated, and return it to the parchment-lined baking sheet.
Once all the patties are dipped, place them back in the refrigerator for another 10 minutes, allowing the chocolate to set.
Serve chilled or at room temperature and enjoy your homemade peppermint patties!