Preheat the oven to 300F. Butter and flour a 9x13 baking dish; set aside. Combine the flour, cocoa powder, and salt in a small bowl; set aside.
In an electric mixer, cream the butter and sugars until light and fluffy, about 2 minutes. With the mixer on low, slowly add the flour mixture and mix until the flour is completely incorporated. Stir in the chocolate chips.
Press the dough evenly into the baking dish and bake for about 35 to 40 minutes, or until a cake tester comes out clean. Allow the bars to cool completely before proceeding.
To make the frosting: Cream the butter in an electric mixer. Add the confectioners' sugar, milk, and peppermint extract and beat until light and fluffy. If you would like the frosting to be pink, add one or two drops of red food paste. If the frosting seems too thick add more milk by the tablespoonful until the desired thickness is reached.
Spread the fresh buttercream on the bars. Scatter the crushed candy canes on top of the frosting and drizzle with the melted chocolate. Cut into squares and serve.
If you like, line your baking pan with foil, extending the foil over edges of pan. Grease foil; set pan aside. For easy removal after baking and spreading with frosting, simply use the edges of the foil to lift the uncut bars out of the pan.