Using a blender or a food processor, finely chop 1/3 cup semisweet chocolate chips. Place in a small mixing bowl. Add vanilla wafer crumbs, ground hazelnuts, 2 tablespoons white sugar, and melted butter or margarine. Mix until well combined. Press onto the bottom and up the sides of a 9 inch springform pan. Bake in a preheated 300 degrees F (150 degrees C) oven for 15 minutes. Cool.
In a large bowl, beat the cream cheese until fluffy. Gradually add 1 cup white sugar; mix well. Add the eggs and 3 tablespoons liqueur. Mix until well blended. Coarsely chop 1 cup of the semisweet chocolate chips, and add to the cream cheese mixture. Stir. Pour batter into the cooled crust.
Bake at in a preheated 350 degrees F (175 degrees C) oven for 1 hour. Let cake cool for 1 hour. Remove outer ring from pan. Then let cool completely.
Melt 2/3 cup semisweet chocolate chips over hot (not boiling) water. Stir until smooth. Dip 13 hazelnuts into the chocolate, covering one-half of each nut. Shake off the excess chocolate. Place on a waxed-paper lined plate. Chill until set.
To the remaining melted chocolate, add sour cream. Mix well. Stir in 1 tablespoon liqueur. Spread glaze on top of the cooled cheesecake. Garnish with chocolate dipped hazelnuts.
