Microwave 4 of the chocolate squares, 6 Tbs. of butter and the water in a large microwave bowl on high 2 minutes or until butter is melted; stir.
Add dry pudding mix; stir until well blended.
Add powdered sugar, 1 cup at a time, stirring until well blended after each addition. Press into foil-lined 8-inch square pan.
Microwave remaining 4 chocolate squares and 2 tablespoons butter in large microwaveable bowl on high 1-1/2 minutes or until butter is melted. Stir until chocolate is completely melted. Spread over pudding mixture.