Preheat oven to 350º. Line a 9 x 9 inch baking pan with parchment paper and spray with cooking spray.
Melt the butter and bittersweet chocolate chips together in the microwave on 50% power for 2 minutes stirring every 30 seconds until just melted.
Beat together the eggs, sugar, peppermint extract and vanilla until smooth. Add the cooled chocolate mixture and continue mixing until well blended.
Add sifted flour and salt to the batter, mixing gently until well combined and no trace of the dry ingredients remain. Stir in white chocolate chips by hand.
Spread the brownie batter evenly in the prepared baking pan and bake for 20-25 minutes or until a toothpick inserted in the center comes out clean or with only crumbs, not batter, on it. Remove from the oven and let cool on a rack for 30-60 minutes.
While the brownies cool, put the candy canes in a plastic bag, cover with a towel, and pound with a hammer or rolling pin until the candy is crushed in to tiny pieces.
Icing: melt the white chocolate chips in the microwave on 50% power for 11/2 minutes stirring every 30 seconds until just starting to melt. Add the powdered sugar and whisk the icing until smooth, add a small amount of milk/cream as needed. It should be fairly thick.
Once the brownies are cool, spread the icing over the top of the brownies in the pan. You do not have to be perfect and go to the ends; you can dab some here and there. Immediately sprinkle the candy cane bits on top and refrigerate for 30 minutes or until the topping is set. cut just before serving.