Preheat the oven to 350°F (175°C). Grease and line an 8x8-inch square baking pan with parchment paper.
Combine the melted butter and chopped dark chocolate in a large mixing bowl and stir until smooth.
Whisk in the granulated sugar and brown sugar until fully incorporated.
Add the eggs one at a time, whisking vigorously after each addition until the batter is glossy.
Stir in the vanilla extract and peppermint extract.
Sift the flour, cocoa powder, and salt directly into the wet ingredients and fold until just combined.
Pour the batter into the prepared baking pan and spread evenly.
Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Immediately sprinkle the crushed peppermint candy canes over the surface of the hot brownies.
Allow the brownies to cool completely in the pan before lifting them out for slicing.