It may seem odd to eat peppermint sweets post-December, but this combination of dark chocolate cookie and semisweet coating is a year-round affair. Delicious at room temperature, our take on a Girl Scout Thin Mint may be even better straight from the freezer.
Special equipment: We’re assuming that you have basic tools like a rubber spatula, bowls, and measuring cups. The other items you’ll need are a kitchen scale and a chocolate thermometer such as CDN’s.
What to buy: For this recipe, we preferred the pure minty flavor of peppermint oil rather than peppermint extract, which has a slightly chemical aftertaste. Peppermint oil can purchased at many nutrition stores or online.
Professional pastry chefs use a type of chocolate known as couverture, which sets up nicely because it contains more cocoa butter than regular chocolate. The only trick is, you need to temper it. For this recipe, we used El Rey 58.5 percent dark chocolate Discos; they can be found at many specialty grocery stores or online.
Game plan: The cookies can be baked up to 24 hours in advance and stored in an airtight container until ready to coat.
In our experience, it’s best to avoid tempering chocolate on a hot day or to work in an air-conditioned space. Chocolate behaves best at a room temperature between the mid-60s and low 70s. Also, chocolate stays in temper for only a short time, so have everything ready to go and work quickly.
For an illustrated guide to making these cookies, see our Slim Mints project.
- 1Place egg yolk, peppermint oil, and vanilla extract in a small bowl and whisk to break up the yolk.
- 2Combine 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.
- 3Turn 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.
- 4Heat the oven to 350°F and arrange a rack in the middle. Line a baking sheet with parchment paper; set aside.
- 5Remove 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.
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. (You can use the same piece of parchment paper.)
For the coating:
- 1Line two baking sheets with parchment paper; set aside.
- 2Prepare an ice water bath by filling a large bowl with 2 inches of cold water and adding 3 to 4 ice cubes; set aside.
- 3Bring a medium saucepan filled with 1 to 2 inches of water to a simmer over high heat; once simmering, turn off the heat. Place 24 ounces of the chocolate couverture in a dry, heatproof bowl. Set the bowl over the saucepan and stir until the chocolate is completely melted and has reached 118°F. (Make sure the chocolate does not come in contact with water or exceed 120°F. If either happens, start over, as the chocolate will no longer be usable.)
- 4Remove the bowl from the saucepan. Add the remaining 8 ounces chocolate and stir until all the chocolate has melted and the temperature has cooled to 80°F. To speed up the cooling process—but only after all of the chocolate has melted—place the bowl over the reserved ice water bath.
- 5Once cooled, return the bowl of chocolate to the saucepan and stir until the chocolate reaches 88°F; immediately remove from heat. Do not remove the thermometer from the bowl; check the temperature periodically to make sure it stays between 87°F and 89°F. (The chocolate must remain in this temperature range while dipping the cookies or it will not set properly.) Keep the saucepan of water over low heat and, when needed, set the bowl of chocolate over it to reheat.
- 6To test if the chocolate is properly tempered, spread a thin layer on parchment paper and place it in the refrigerator for 3 minutes to set. If the chocolate hardens smooth and without streaks, it is properly tempered. (If it is not properly tempered, let the melted chocolate harden and start the tempering process over again: Bring the chocolate up to 118°F, then down to 80°F, then up again to 88°F.)
- 7Using a dinner fork, dip the cooled cookies one at a time into the chocolate until covered. Lift each cookie out of the chocolate and tap the fork several times on the edge of the bowl. Scrape the bottom of the fork against the edge of the bowl to remove any excess chocolate.
- 8Place the cookies on the prepared baking sheets by tilting the fork so that the edge of each cookie touches the parchment-lined pan, then pull the fork out. Repeat until all the cookies have been dipped. Let sit at room temperature until completely set, about 20 minutes.
Store in an airtight container at room temperature for 1 week or in the freezer for up to 1 month.