In a large bowl, combine 8 cups of confectioners' sugar, corn syrup, water, peppermint extract, butter, and salt. Mix until a smooth dough forms.
Roll out the dough on a surface dusted with the remaining confectioners' sugar to about 1/4-inch thickness. Use a round cookie cutter to cut out patties.
Place the patties on a parchment-lined baking sheet and chill in the freezer for about 30 minutes.
In a microwave-safe bowl, melt the chocolate chips and vegetable oil in 15-second intervals, stirring until smooth.
Using a fork, dip each chilled patty into the melted chocolate, tapping off any excess.
Place the coated patties back on the baking sheet and chill in the freezer for at least 10 minutes until set.
Enjoy these homemade Peppermint Patties as a delightful treat!