Preheat oven to 350°F and line a 9x9-inch baking pan with parchment paper.
In a mixing bowl, prepare the brownie mix according to the package instructions then stir in the peppermint extract.
1 box fudge brownie mix, 1 teaspoon peppermint extract
Pour the batter into the prepared pan and bake as directed on the box.
When the brownies come out of the oven, make the topping.
In a microwave-safe bowl, stir together the white chocolate and heavy cream.
12 ounces white chocolate chips, 1/4 cup heavy whipping cream
Heat in 20-30 second intervals, stirring well after each burst, until smooth.
Stir in the crushed peppermint candies.
1/4 cup crushed candy canes or peppermint candies
Spread the mixture over the prepared brownies and sprinkle additional crushed candies on top.
Let cool completely before removing from the pan and cutting into squares.