Preheat oven to 350°F. Line an 8x8 square pan with foil and spray with nonstick baking spray. Set aside.
In a large bowl, whisk butter and cocoa powder together until cocoa is dissolved and mixture is thick.
Stir in sugar until combined. Stir in eggs, mixing until combined.
Add peppermint and vanilla extracts.
Add flour, stirring just until no white streaks remain in batter.
Fold in melted chocolate and white chocolate chips.
Pour batter in prepared pan and spread evenly.
Bake for about 25 minutes, or until a toothpick inserted in the center comes out with fudgy crumbs, but not raw batter.
Let cool to room temperature.
In the bowl of your mixer, beat butter and heavy cream on medium speed until combined.
Add powdered sugar and beat on low until just barely mixed.
Add crushed peppermint candies and beat on high speed for one minute.
Frost cooled brownies and refrigerate for one hour.
In a microwave safe bowl, heat chocolate chips and heavy cream for about a minute and a half, stopping to stir every 30 seconds until smooth.
Add corn syrup and stir to combine.
Let ganache cool to room temperature, then spread over frosted brownies.
Sprinkle with crushed candy and drizzle with white chocolate.