Prepare cake mix according to package directions, using required ingredients, plus pudding mix, vanilla, and an additional 1/4 cup of water. Spread batter evenly among three greased and floured 9 inch cake pans. Bake at temperature specified on cake mix box for 18 to 22 minutes, or until a toothpick inserted in the center comes out clean. Let cakes cool completely, then chill in refrigerator for 30 minutes.
In a double boiler over simmering water, melt chocolate chips. Gradually add 1/4 cup of the whipping cream, stirring constantly until smooth. Remove from heat and let cool to room temperature. Beat 3/4 cup of whipping cream until soft peaks form. Fold the whipped cream into the cooled chocolate mixture. Stir in 1/2 cup of the finely chopped hazelnuts. Chill 30 minutes.
Beat remaining 2 cups of whipping cream until soft peaks form, then fold in the remaining 1/2 cup of chopped hazelnuts. Chill until ready to frost cake.
Place 1 cake layer on cake plate. Spread 1/2 of the chilled chocolate mixture over top. Add another cake layer. Spread with other 1/2 of chocolate mixture. Top with last cake layer. Frost entire cake with hazelnut-whipped cream. Place 12 whole hazelnuts around top outer edge of cake as a garnish. This cake should be kept in the refrigerator.
