Preheat oven to 400 degrees.
Bake pastry sheets according to package directions.
In a medium size bowl, combine chocolate pudding mix and 1 1/2 c milk.
Whisk until thickened, then fold in whipped topping.
Spread over 1 layer of pastry, then place the other pastry, flat side up, on top of the pudding.
Place a cookie sheet on top and press down to flatten the pastry.
In a medium size bowl, whisk the powdered sugar and remaining 1/4 c milk until a smooth icing is formed.
Reserve two T icing; set aside.
Pour remaining icing over the top and spread to the edges.
Stir the cocoa powder into the remaining icing until well blended.
Drizzle over the white icing.
Freeze for four hours.
Cut into squares and serve.