In a large bowl, cream 8 tablespoon butter, vanilla and 1/3 cup confectioners’ sugar until light and fluffy.
Combine flour, salt and cornstarch; gradually add to creamed mixture. And mix until combined (some crumbs are OK).
Remove half of the dough and set aside.
To the dough still in the bowl add the candy cane bits and mix just until combined.
Pat the dough into the pan.
In a clean bowl add the remaining dough and 4 tablespoon butter, 1/4 cup confectioners’ sugar, cocoa and mini chips. Mix to combine.
Pat that dough carefully on top of the other dough in the pan. You want to layer this. Pierce several times with a fork. Bake at 35-40 minutes or until lightly firm to the touch. A little give is OK but not much.
Remove from the oven, allow to set for 10 minutes then with a very thin firm spatula loosen the edges and then invert onto a cooling rack. Cut while warm
Cool completely. Once cooled dip the chocolate crust into the melted dark chocolate and place on cooling rack, chocolate side up to firm.