Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, 1/2 cup sugar, 2 Tbsp. cocoa, baking powder, and salt in a bowl, stirring with a whisk. Add milk, butter, and vanilla; stir until just combined. Scrape batter into a 9- x 9-inch metal baking pan coated with baking spray. Combine 1/4 cup sugar, 2 Tbsp. cocoa, and brown sugar; sprinkle mixture over top of batter. Carefully pour coffee over top. (Do not stir in.)
Bake at 350° for 28 to 30 minutes or until just set. (Do not overbake.) Let stand 10 minutes; top with whipped topping.
Cooking Light Incredibly Decadent Desserts by Deb Wise, copyright 2015, Oxmoor House.