Preheat the oven to 350°F. Line a 9x9-inch baking dish with parchment paper. Be sure to leave an overlap or “sling” of parchment paper. Set it aside.
Whisk together 1 cup of flour and unsweetened cocoa powder in a small mixing bowl. Set it aside.
Toss the chocolate chunks in the 1 tablespoon of flour. Remove the excess flour and set it aside.
Using a 2 to 3-quart saucepan over low heat, add the butter and chopped baking chocolate. Stir constantly until the butter and chocolate are completely melted. Transfer the chocolate mixture to a large mixing bowl to cool. (The mixture won’t be hot, just slightly warm.)
Whisk the granulated sugar and vanilla into the cooled chocolate and butter.
Whisk in the eggs, one at a time, until well combined.
Stir in the cocoa and flour mixture, and be sure not to over-mix, just until no streaks of flour are visible.
Fold in the flour-coated chocolate chunks.
Spoon in and evenly spread the brownie batter into the prepared baking dish. Bake for 30 to 35 minutes, or until a toothpick inserted comes away with only a slight bit of brownie crumbs. Allow the brownies to rest for 5 minutes.
Sprinkle the chopped candy bars over the top of the brownies. (I sprinkled the larger chopped pieces first and ended with the Whoppers). Allow the brownies to cool completely before slicing and serving.