In a mixing bowl, combine powdered sugar, sweetened condensed milk, and peppermint oil (or extract). Mix until a soft dough forms. Add more sugar if too sticky.

Roll the peppermint mixture into small balls, flatten into discs, and place on a parchment-lined tray. Freeze for 10–15 minutes.

While patties chill, melt chocolate chips and optional coconut oil in a microwave-safe bowl or double boiler until smooth.

Dip each chilled disc into melted chocolate, coating completely. Let excess drip off.

Place coated patties back on the tray and refrigerate until chocolate is firm, about 5 minutes.