Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper or grease it well.
In a medium saucepan over low heat, melt the unsalted butter until fully liquid. Remove from heat and stir in granulated and brown sugars until combined. Let cool slightly.
Add eggs one at a time, mixing well after each addition, then stir in vanilla extract.
In a separate bowl, sift together cocoa powder, flour, and salt. Gradually fold this dry mixture into the wet ingredients until just combined.
Pour the batter into the prepared pan and bake for 25-30 minutes or until a toothpick inserted comes out with moist crumbs.
Remove from oven and sprinkle crushed candy canes on top while warm. Let cool before slicing.
