1) Preheat oven to 350°F. Coat a 13x9-inch baking pan with non- stick cooking spray. Line with parchment paper.
2) For the brownies, in a microwave safe bowl, combine chocolate and butter. Melt on high heat for 1 minute, stir and melt for 30 seconds more or until the chocolate and butter are melted and smooth.
3) In a large bowl, whisk sugar and eggs. Add chocolate mixture and flour, stirring until flour has disappeared. Spread in prepared pan and bake 25-30 minutes. Let cool in pan for 15 minutes before removing. Cool completely on wire rack before frosting.
4) For the frosting, in a large saucepan, mix together sugar, cocoa powder, milk, butter and corn syrup. Heat to boiling, stirring frequently. Boil for 3 minutes, stirring constantly. Cool for 10 minutes. Whisk in icing sugar until smooth.