In small bowl, beat egg yolks with fork. Gradually add about 1/4 of the melted chocolate mixture to the egg yolks, stirring constantly. Stir egg mixture back into the pan of hot chocolate cream. Cook over medium-low heat, stirring constantly for 3 to 5 minutes until mixture begins to thicken; remove from heat. Spread 1/2 cup of the chocolate mixture in bottom of cooled crust. Press 1 cup of the toasted hazelnuts into hot filling. Carefully spoon remaining chocolate filling over nuts. Refrigerate at least 1 hour or until completely cooled.