Preheat oven to 350 degrees F (175 degrees C). Grease and flour an 8x8 inch pan.
In a small saucepan over medium heat, melt margarine and cocoa together, stirring occasionally until smooth. Remove from heat and set aside to cool. In a large bowl, beat eggs until frothy. Stir in the sucrolose sweetener. Combine the flour and salt; stir into the egg mixture then mix in the cocoa and margarine. Finally stir in the milk and if desired, the walnuts. Pour into the prepared pan.
Bake for 25 to 30 minutes in the preheated oven, until a toothpick inserted into the center, comes out clean. To make frosting, Mix together the sugar free chocolate pudding mix and 1 cup skim milk using an electric mixer. Mix for about two minutes or until thick. Spread over cooled brownies before cutting into squares.