Add margarine, cocoa and water together in a saucepan and heat until the margarine is melted and the cocoa is dissolved
Let the cocoa mixture cool slightly then add the sugar and eggs, mix well
Add the baking soda, salt and flour, mixing until smooth, then add the sour cream and combine
Grease an 11" x 16" x 1" cookie sheet and pour the batter onto the sheet
Bake at 350° for approximately 20 minutes, or until center of pan is set
Let cool slightly before icing
For the Icing
Melt the margarine in a pan, add milk and cocoa powder stir until dissolved
Remove from heat and add the vanilla and icing sugar, mix until well combined
Notes
Mix icing after the brownies com out of the oven. You want to ice while they are warm, but not hot out of the oven.These freeze great (so you don't eat the whole pan in one sitting) and are almost better directly from the freezer!