Preheat oven to 350 F. Spray 8" square pan with cooking oil.
For the brownies, combine sugar, oil, egg and vanilla in a bowl and mix well. Add cocoa, and mix it in well. Add flour, baking powder, yogurt (or sour cream) and chocolate chips mixing just until combined and smooth. Dont over mix.
Pour batter into prepared pan. Bke in the center of the oven for 15 - 20 mins, just until set. Dont over bake. Cool on a rack for 15 mins before icing.
~ Icing ~
Place cream cheese, icing sugar, 1 1/2 t cocoa powder and water in a blender or food processor and process until smooth. Sprend over top of the brownies.
Cut into squares, garnish with a dusting of icing sugar or drizzle melted dark and white chocolate over top.