Preheat oven to 350°F (180°C). Grease an 8-in. square baking dish. Using an electric mixer (stand or hand-held) on medium, cream sugar and butter until light and fluffy, about 5 min. Beat in eggs, one at a time, until well combined, about 2 min.
In another bowl, whisk together flour, cocoa and salt. With mixer on low, add flour mixture to butter mixture and mix just until combined. Stir in chocolate chips. Spread batter in prepared baking dish and bake until a toothpick comes out with a few crumbs attached, about 20 min. Let cool completely then evenly spread frosting over brownies, sprinkle with candy canes.
To make neat squares, place cooled pan of brownies in the freezer for about 15 minutes to firm up, then cut with a sharp kitchen knife.