Best Ever Chocolate Fudge Layer Cake (from Kraft) (Robin B.)

1 pkg. (8 squares) Semi-Sweet Chocolate, divided
1 pkg. (2-layer size) chocolate cake mix
1 pkg. (4-serving size) JELL-O Chocolate Instant Pudding
4 eggs
1 cup Sour Cream
1/2 cup oil
1/2 cup water
1 tub (8 oz.) frozen COOL WHIP Whipped Topping
PREHEAT oven to 350°F. Grease two 9-inch round baking pans. Chop 2 of the chocolate squares; set aside. Beat cake mix, dry pudding mix, eggs, sour cream, oil and water in large bowl with electric mixer on low speed just until moistened. Beat on medium speed 2 min. Stir in chopped chocolate. Spoon into prepared pans.
BAKE 30 to 35 min. or until wooden toothpick inserted in centers comes out clean. Cool in pans on wire racks 10 min. Loosen cakes from sides of pans. Invert onto racks; gently remove pans. Cool cakes completely.
PLACE frozen whipped topping and remaining 6 chocolate squares in microwaveable bowl. Microwave on HIGH 1-1/2 min. or until chocolate is completely melted and mixture is smooth, stirring after 1 min. Let stand 15 min. to thicken. Place one cake layer on serving plate; top with one-fourth of the chocolate mixture and second cake layer. Spread top and side with remaining chocolate mixture. Store leftovers in refrigerator.