Ingredients

• 1 ²⁄₃ cups flour
• 1 cup plus 1 tbsp. Dutch-process cocoa powder
• 2 tsp. baking soda
• 1 ³⁄₄ cups sugar
• 12 tbsp. unsalted butter
• ¹⁄₂ cup packed dark brown sugar
• ¹⁄₄ cup vegetable shortening
• 3 tsp. kosher salt
• 1 tsp. vanilla paste, such as Nielsen-Massey
• 1 tsp. mint extract
• 2 eggs
• 12 ¹⁄₂ oz. milk chocolate, chopped into rough chunks
• 2 large peppermint candy canes, chopped into very small, uneven pieces, plus 3 left whole

Instructions

1. Whisk together flour, cocoa, and baking soda in a bowl; set aside. In another bowl, beat ¾ cup sugar, butter, brown sugar, shortening, 2 ¼ tsp. salt, vanilla paste, and mint extract on medium-high speed of a hand mixer until pale and fluffy, about 3-4 minutes. Add eggs one at a time, and beat until smooth. Add dry ingredients, and mix until just combined. Stir in chocolate and chopped candy canes; transfer to a work surface and shape into a ½"-thick square; wrap with plastic wrap and freeze until firm, at least 4 hours or overnight. Meanwhile, combine remaining sugar and salt with candy canes in a food processor, and process until finely ground; transfer to a bowl and set peppermint sugar aside.
2. Heat oven to 425°. Cut dough into 1 ½" squares and toss in peppermint sugar to coat, and place 2" apart on parchment paper-lined baking sheets. Sprinkle remaining peppermint sugar on tops of squares and return to freezer for 30 minutes. Bake until spread and just set and tops are lightly cracked, about 8 minutes.