Chocolate Mint Cookies (Makes about 5 dozen cookies)
For the cookies:
1 large egg yolk
1/2 teaspoon peppermint extract
1/2 teaspoon pure vanilla extract
1 3/4 cups all-purpose flour
1 cup powdered sugar
1/2 cup unsweetened Dutch-processed cocoa powder
1/4 teaspoon kosher salt
2 sticks (8 ounces) unsalted butter, chilled and cut into small pieces
For the coating:
7 ounces semisweet chocolate
To make the cookies:
1. Place egg yolk, peppermint extract, and vanilla extract in a small bowl and whisk to break up the yolk.
2. Combine flour, sugar, cocoa powder, and salt in the bowl of a food processor fitted with a blade attachment and pulse a few times to aerate and break up any lumps. Add butter and pulse until the mixture looks like sand, about 25 1-second pulses. Add yolk mixture and pulse just until the dough forms into a ball, about 15 1-second pulses.
3. Turn dough out onto a clean work surface and roll into 2 logs, each about 1 1/2 inches in diameter. Wrap the logs in plastic wrap and refrigerate until just firm but still pliable, about 1 hour. (The logs will flatten slightly while chilling. If you have a paper towel tube available, cut it in half lengthwise and nestle the cookie dough in there; this will help the dough keep its cylindrical shape while it chills.) Reshape the logs so they are perfectly round and refrigerate until firm, about 1 hour more.
4. Heat the oven to 350°F and arrange a rack in the middle. Line a baking sheet with parchment paper; set aside.
5. Remove a dough log from the refrigerator, remove the plastic wrap, and slice the dough into 1/8-inch coins. Place the cookies 1/2 inch apart on the prepared baking sheet. (About 30 cookies will fit on 1 sheet.) Rewrap the extra cookie dough in plastic and refrigerate until ready to bake the second batch.
6. Bake the cookies until the edges are firm but the tops are still soft, about 9 to 11 minutes. Remove to a wire rack to cool completely. Repeat with the remaining dough.
To make the (non-tempered) chocolate coating for dipping:
Put 3 ounces of the chocolate in a glass bowl and microwave on high power for about 30 seconds. Stir with a wooden spoon. Continue to heat and stir in 30-second increments until the chocolate is just melted. Add the remaining chocolate and allow it to sit at room temperature, stirring often, until it’s completely smooth. Stir vigorously until the chocolate is smooth and slightly cooled; stirring makes it glossier.
Taking one cookie at a time, dip one end of each cookie in the melted chocolate and place it on a parchment paper lined sheet pan. Once all the cookies have been dipped, place the sheet pans in the refrigerator for about 10 minutes, or until the chocolate has hardened.