2 cups all-purpose flour 1 teaspoon cornstarch 1 teaspoon baking soda ½ teaspoon salt 1½ sticks unsalted butter, softened to room temperature ½ cup packed light brown sugar ½ cup granulated sugar 1 large egg, at room temperature 1 teaspoon pure vanilla extract 1½ teaspoons peppermint extract 1 cup white chocolate chips ½ cup crushed candy cane pieces (5 candy canes) 4 ounces white chocolate, coarsely chopped
In a large mixing bowl, whisk together flour, cornstarch, baking soda, and salt.
In a stand mixer with paddle attachment, beat butter for 1 minute on medium speed until completely smooth and creamy. Add brown sugar and granulated sugar, and mix on medium speed until fluffy and light in color. Add egg, vanilla extract, and peppermint extract. Scrape down the sides and bottom of the bowl as needed.
On low speed, slowly mix the dry ingredients into the wet until combined. The cookie dough will be very thick. Add white chocolate chips and crushed candy canes, then mix for about 5 seconds until combined. Cover dough tightly with plastic wrap and chill for at least 2 hours or overnight.
Remove cookie dough from the refrigerator and allow to sit at room temperature for 10 minutes. Preheat oven to 350°. Line 2 large baking sheets with parchment paper or silicone mats.
Roll dough into individual balls, about 1½ tablespoons each. Dough may be crumbly.
Bake for 12 minutes, until light golden brown around the edges. Allow to cool for 5 minutes on the cookie sheet, then transfer to a wire rack to cool completely.
Microwave chopped white chocolate in 20-second increments, stirring after each until completely melted. Use tines of a fork to drizzle over cooled cookies. Store in an airtight container.