Peppermint Chocolate Cookies

1 1/2 stick (6 ounces) unsalted butter, softened
1 1/2 cups confectioners’ sugar
1 large egg
1 1/2 cups flour
1/2 cup unsweetened cocoa powder
1 pinch salt
Two 3.5 -ounce bars dark chocolate, finely chopped - I used dark chocolate chips
1/2 teaspoon vegetable oil
2/3 cup finely crushed peppermint candy canes or candies

Using an electric mixer, beat the butter until soft. With the mixer on low, gradually add the confectioners’ sugar until creamy, then beat in the egg. In a medium bowl, whisk together the flour, cocoa and salt; add to the mixer about one-third at a time, beating at low speed until smooth.

Lay a 16-inch sheet of parchment paper on a work surface; turn out the dough onto the paper. Using your hands, shape the dough into a 12-inch-long cylinder; wrap tightly in the parchment and roll into a smooth, even log. Twist the ends to seal and refrigerate for 30 minutes; reshape the cylinder and refrigerate for 30 minutes more.

Preheat the oven to 350°; line 2 cookie sheets with parchment paper. Unwrap the dough; using a sharp knife, slice into 1/3-inch-thick rounds. Place about 1 inch apart on the cookie sheets; bake until firm, 18 to 20 minutes. Let cool completely.

In a bowl, combine two-thirds of the chopped chocolate with the oil; microwave for 30 seconds, then stir until smooth. (If needed, heat for additional 10-second intervals.) Stir in the remaining chopped chocolate until smooth.

Using an offset spatula (I used the back of the spoon I used to stir the chocolate), spread a scant teaspoon of melted chocolate on top of each cookie. Sprinkle the peppermints on top and let stand until set, 2 to 3 hours.