For cake:
Cook water, oil and cocoa until margarine is melted. Add remaining ingredients. Put in jelly roll pan and bake at 350 degrees for 20-25 minutes. Cool completely.
For filling:
Mix sugar, shortening and milk for 5 minutes with electric mixer. Add powdered sugar and vanilla. Spread on cooled cake.
For frosting:
Bring sugar, margarine and milk to a boil. Boil 1 minute. Add chips, beat till slightly thick and somewhat cooled (So frosting doesn't melt filling). Spread on cake.