Preheat your oven to 350 degrees F. Spray a 9x13 inch baking dish. Line the bottom of the pan with parchment paper creating a sling with some hanging over the side.
Using an electric mixer, beat together the butter and sugar until light and fluffy. Beat in the vanilla extract then the egg yolk.
Gradually add in the flour and sea salt and continue to beat until a thick dough forms.
Drop the dough by spoonfuls all over the prepared dish. Using your fingertips, press dough all over the pan until you form an even layer. Puncture the dough with a fork all over to prevent it from bubbling.
Transfer the pan to the oven and bake the cookie dough layer for about 27 minutes, or until the edges are lightly golden.
Remove from oven and immediately scatter the chocolate chips all over the hot dough. Let it melt for a few minutes, then spread the melted chocolate evenly all over the cookie layer with a spatula. Immediately sprinkle the chopped kisses or candy canes all over the chocolate layer.
Refrigerate for a few hours, or until chocolate and kisses are firm and chilled. Remove from the fridge, and lift the entire cookie sheet out of the baking dish. Cut into irregular pieces.