Preheat your oven to 350°F. While it heats, spray a 9x13 inch baking dish with cooking spray and line it with parchment paper, leaving some overhang on the sides for easy removal later. Chop your candy cane kisses into 1/4 to 1/2-inch pieces and set aside—I like to do this first so the pieces are ready when you need them, and you won't have sticky candy fingers later in the process. Measure out your flour and salt into a small bowl.

In a large mixing bowl, beat the softened butter and sugar together until the mixture is light, fluffy, and pale—this usually takes about 2-3 minutes and is crucial for creating a tender cookie texture. Add the vanilla extract and egg yolk, beating until fully incorporated and the mixture looks smooth. Add the dry ingredient mixture (flour and salt from Step 1) and beat until a thick, cohesive dough forms. The dough should come together completely with no visible flour streaks.

Transfer the dough from Step 2 into your prepared baking dish and use your hands or an offset spatula to press it into an even, compact layer covering the entire bottom. Pierce the dough all over with a fork—this prevents large air pockets from forming and helps the base bake evenly. Bake for 27 minutes, or until the edges are golden brown and the surface is set but still slightly soft to the touch.

Remove the hot cookie base from the oven and immediately scatter the chocolate chips evenly over the surface. Let them sit for 1-2 minutes to soften from the residual heat, then use an offset spatula or the back of a spoon to spread the melted chocolate into an even layer. While the chocolate is still warm and slightly tacky, sprinkle the chopped candy cane pieces generously over the top, pressing them gently so they adhere to the chocolate.

Transfer the entire baking dish to the refrigerator and chill until the chocolate is completely firm and set—about 30-45 minutes. Once chilled, use the parchment paper overhang to lift the entire cookie slab out of the dish onto a cutting board. Cut into squares or rectangles using a sharp knife, wiping the blade between cuts if needed to keep them clean.