Preheat oven to 350 degrees F. For crust, prepare brownie mix according to package directons. Spread in the bottom of a greased 9-inch pie plate. Bake 20 to 25 minutes or until wooden toothpick, inserted near center, comes out clean. Cool on wire rack.
For filling, in a medium mixing bowl beat sugar and butter with an electric mixer on medium speed about 4 minutes or until fluffy. Stir in melted and cooled chocolate and the vanilla. Gradually add egg product, beating at low speed until combined. Then beat on medium to high speed, scraping sides of bowl about 1 minute or until light and fluffy.
Transfer filling to prepared pie plate. Cover; chill for 4 to 24 hours. To serve, spread with sweetened whipped cream and sprinkle with shaved chocolate. Cut into wedges. Makes 10 servings.