Mix together dry ingredients - cocoa, flour, baking powder and salt. Set aside.
Using a hand mixer, mix sugar and melted butter. Add vanilla extract and eggs. Mix.
Slowly add dry ingredients while mixing. Batter will be thick.
Line an 8x8 baking dish with foil, press foil down firmly into the dish. Spray with non-stick.
Pour batter into prepared dish and spread evenly.
Bake at 350° for 30-35 minutes. (until a toothpick can be inserted a removed clean)
Allow brownies to cool before frosting.
Once cooled, spread frosting evenly over the top. Remove the foil and brownies from baking dish. Carefully peel foil away from brownies. Slice into 9 pieces (or more).
Frosting
Mix butter and shortening. Gradually add in powdered sugar and heavy cream. Mix for 3-4 minutes, or until light and fluffy (stop to scrape sides as needed).