Preheat oven to 350°F. Microwave chocolate and butter in large microwavable bowl on HIGH 2 minutes or until butter is melted. Stir until chocolate is completely melted. Add sugar, eggs and vanilla; mix until well blended. Stir in flour and nuts. Spread into greased 9-inch pie plate.
Bake 25 minutes or until toothpick inserted in center comes out with fudgy crumbs. DO NOT OVERBAKE. Cool completely on wire rack.
Pour milk into large bowl. Add dry pudding mixes. Beat with wire whisk 2 minutes. Let stand 2 minutes. Spread over pie. Top with whipped topping; sprinkle with grated chocolate. Refrigerate until ready to serve. Store leftover pie in refrigerator.