1/2cupcrushed red-and-white-striped candy canes or hard peppermint candies, about 4 oz. (115 g)
Instructions
For Cookies:
Whisk together the flour, cocoa, and salt in a medium bowl. Using an electric mixer, beat the sugar and butter in a large bowl until well blended. Beat in the egg. Add the dry ingredients and beat until blended. Refrigerate the dough for 1 hour.
Preheat the oven to 350°F (176°C). Line 2 baking sheets with parchment paper. Scoop out the dough by level tablespoonfuls, then roll it into smooth balls. Place the balls on the prepared baking sheets, spacing them about 2 inches (5 cm) apart. Using the bottom of a glass or your hands, flatten each ball into a 2-inch (5 cm) round (the edges may crack).
Bake until the cookies no longer look wet and a small indentation appears when the tops are lightly touched with your fingers, about 11 minutes (do not overbake, or the cookies will become too crisp). Cool on the baking sheet for 5 minutes. Transfer the chocolate cookies to wire racks to cool completely.
For Filling:
Using an electric mixer, beat the powdered sugar and butter in a medium bowl until well blended. Add the peppermint extract and 2 drops of food coloring. Beat until the mixture is light pink and well blended, adding more food coloring drop by drop if a darker pink color is desired.
Spread 2 generous teaspoons of the filling evenly over the flat side of 1 cookie, reaching the edges. Top with another cookie, flat side down, and press gently to adhere. Repeat with the remaining cookies and peppermint filling.
Place the crushed candy canes on a plate. Roll the edges of the cookie sandwiches in the crushed candies, allowing them to adhere to the filling.
Notes
Cookie sandwiches can be made ahead. Store in single layer in airtight container at room temperature up to 3 days or freeze up to 2 weeks.