Preparation

• Preheat the oven to 350 degrees. Line an 8-inch square cake pan.
• In a large mixing bowl, cream the granulated sugar and ½ cup butter with an electric mixer on high speed until fluffy and light, about 5 minutes.
• Add the egg and yolk and beat on high speed, stopping once to scrape down the sides and bottom of the bowl. Add 1 teaspoon peppermint extract and a pinch of salt and beat until combined.
• Add the flour, candy cane pieces, cornstarch, baking powder and baking soda and fold in with a spatula until even and there are no white streaks.
• Pour the batter evenly into the cake pan. Bake 25 minutes, until it is browned on top but still soft. Let cool completely.
• To make the frosting, place the powdered sugar, the remaining ¾ cup butter, milk, the remaining 1 teaspoon peppermint extract and a few drops green food coloring in a bowl. Beat the ingredients together on medium-high speed until light and fluffy. Add more peppermint extract or food coloring to taste.
• Spread the frosting in a thick even layer atop the cookie and sprinkle with crushed candy canes.
• Use a sharp knife to cut the cookie into 2-by-2-inch bars. Store in an airtight container at room temperature up to 5 days.