I used my favorite brownie recipe, which is from Hershey's.
Grease 13x9x2 inch baking pan. Heat oven to 350 degrees. Melt butter in microwave. Stir in sugar and vanilla. Beat in eggs, one at a time. Add cocoa, flour, baking powder and salt; beat until well blended. Pour batter into pan.
Bake 30 minutes or until brownies begin to pull away from sides.
If you want to frost them like normal, you can go ahead and do that. I made frosting (1 cup powdered sugar, 3 tablespoons cocoa powder, 1 tablespoon melted butter, 1.5 tsp water), but spread it on while they were still a little warm and then put the pan in the fridge, so it came out a bit more like a smooth glaze. Then I decorated with white decorator's frosting!