First preheat the oven to 350F. Then chop 2 chocolate squares. Beat the cake mix, pudding, eggs, sour cream, oil & water in a large bowl with a mixer until blended. Then stir in the chopped chocolate & pour into 2 9 inch round cake pans sprayed with cooking spray.
Next bake for about 30 to 35 mins or until toothpick insert comes out clean. Cool in the oans for about 10 mins. Then loosen the cakes from the sides of the pans. Flipoveronto a wire rack. Then gently remove the pans. Cool completely.
Next microwave the COOL WHIP & remaining chocolate squares in a microwaveable bowl on high for abotu 1-1/2 mins or until chocolate is completely melted & mixture is well mixed. Then stir after 1 min. Let stand for about 15 mins to thicken.
Then stack the cake layers on a plate, filling & forsting with the COOL WHIP mixture. Then sprinkle with the nuts. Keep refrgerated.