Preheat the oven to 350 degrees F.
Cream 10 tablespoons of the butter with the sugars in a medium bowl, and then beat in the vanilla and egg
yolk. Add the flour and cocoa and beat until smooth. Transfer the dough to wax paper and roll into a 10-by-2-inch log. Wrap and refrigerate 1 hour.
Slice the dough
into 1/4-inch rounds and flatten gently on a baking sheet. Bake 7 to 8 minutes, and then let cool 10 minutes.
Meanwhile, cream the remaining 4 tablespoons butter
with the confectioners' sugar, peppermint
extract and 1 teaspoon of the cream until smooth. Spread about 2 teaspoons of peppermint cream each over half of the cookies
and close with a plain baked cookie.
the chocolate chips
with the remaining cream in a small saucepan
, adding more cream to make it smooth but not runny. Spread over half of the cookies and top with the candy
canes while the chocolate is still wet.