Pour the brownie batter into the prepared baking dish and bake according to the instructions on the box.
Allow the brownies to cool to room temperature before adding the bark topping. (This can even be done the next day).
In a small microwave-safe bowl, melt the white chocolate with ½ teaspoon of coconut oil in the microwave in 15-second intervals, stirring in between. Whisk until smooth.
1 teaspoon coconut oil, 10 ounces white chocolate chips
In another small bowl, repeat the process with the semi-sweet chocolate chips.
Pour the melted chocolate on the brownies, using a butter knife to swirl the white and semi-sweet chocolate together. Before the chocolate sets, sprinkle with the crushed peppermint candies.