Step 1

Preheat an oven to 375°F (190°C). Line a baking sheet with parchment paper.

Step 2

In the bowl of a stand mixer, using a handheld whisk, whisk together the flour, sugar, cocoa powder, baking soda, baking powder and salt. Fit the mixer with the paddle attachment, add the butter and beat on low speed until light and fluffy, about 3 minutes, then beat in the egg, egg yolk and peppermint extract. Raise the speed to medium and beat until the dough comes together, about 2 minutes.

Step 3

Drop the dough by rounded tablespoons onto the prepared baking sheet, spacing the cookies about 2 inches (5 cm) apart. Flatten each ball slightly with the palm of your hand.

Step 4

Bake until the cookies are firm to the touch, 8 to 10 minutes. Transfer the baking sheet to a wire rack and let the cookies cool on the sheet for 5 minutes, then transfer the cookies to the rack and let cool completely.

Step 5

Meanwhile, make the icing: Place the white chocolate chips in a heatproof bowl set over (but not touching) barely simmering water in a saucepan and heat, stirring occasionally, until the chocolate is melted. Remove from the heat and stir in the oil until smooth.

Step 6

Line another baking sheet with parchment paper. Dip each cookie halfway into the melted white chocolate, then immediately sprinkle peppermint candies over the white chocolate. Place on the prepared baking sheet. If the white chocolate begins to harden, set the bowl over simmering water for up to 1 minute to remelt. Let the cookies firm up for at least 15 minutes before serving. Makes about 2 dozen cookies.

Step 7

Adapted from Williams Sonoma Favorite Cookies (Weldon Owen, 2016)