Preheat oven to 350°F. Grease a 9×9 pan and line it with parchment paper. Set aside.
In the microwave or using a double boiler, heat the sweetened condensed milk, butter, and bittersweet chocolate in a large bowl until the butter and chocolate are completely melted. Once melted, allow it to cool for about 10 minutes if it’s too hot.
Add in the granulated sugar, eggs, egg yolk, and vanilla extract. Whisk this for at least a full minute (this is going to help get you the classic crackly brownie top).
Mix in the flour, black cocoa powder, and salt. Whisk until totally combined and batter is smooth.
Pour batter into the prepared pan and spread it evenly. Bake for 36-38 minutes. Once baked, allow the brownies to cool completely before slicing.
Cut cooled brownies into 12 even rectangles. Drizzle the tops with melted white chocolate, and gently press candy eyes in the tops of the brownies. Pop them in the fridge for about 10 minutes to harden the chocolate. Enjoy!