In a small saucepan over low heat, melt the butter and half bag of cocoa baking chips, stirring until melted over very low heat. Let cool. Transfer melted chocolate to a large bowl; add sugar and eggs and beat until smooth. In another bowl, combine flour, cocoa, baking powder and salt. Gradually add the dry ingredients to the chocolate mixture and mix well. Add remainder of chocolate chips to the dough and combine well. Cover and refrigerate for 1 hour until firm. Drop dough by tablespoon full onto greased cookies sheets, 2 inches apart. Bake in a preheated 350 degree oven for about 9-11 minutes, until edges are set. Cool cookies on the pans for about 2 minutes and then transfer to wire racks. After all cookies are cool, heat half and half until hot (not boiling) and take off heat. Add mint chips and stir until melted, just a few minutes. Let cool slightly. In mixer bowl beat butter, add mint/half and half mixture and slowly add just enough confectioners sugar until desired consistency. Spread frosting on cooled cookies, decorate with holiday sugars and enjoy! Store refrigerated in a covered container.