Preheat oven to 350°F. Mix flour, sugar, cocoa & baking soda. Make a hole in the center of the mix. Put remaining ingredients in the hole & mix. Grease & flour 13 x 9 x 2 pan, pour batter into, bake for 35 minutes. Cool cake then ice. Refrigerate cooked cake.
Prepare after cake has cooled then ice cake. Whip flour & milk. Heat on low on stove until thick, stirring constantly. Remove & cool. Beat butter, shortening & sugar until sugar is dissolved and creamy. Add milk mixture. Whip and add vanilla.