Using a blender or a food processor, finely chop 1/3 cup semisweet chocolate chips. Transfer ground chocolate to a 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 preheated oven for 15 minutes. Allow to cool.
Raise oven temperature to 350 degrees F (175 degrees C).
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 stir the chocolate into the cream cheese mixture. Pour batter into the cooled crust.
Bake in preheated 350 degrees F (175 degrees C) oven for 1 hour. Let cake cool in oven for 1 hour. Remove outer ring from pan; allow cake to 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 and chill until set.
Stir the sour cream into the remaining melted chocolate and mix well. Add 1 tablespoon liqueur. Spread glaze on top of the cooled cheesecake. Garnish with chocolate-dipped hazelnuts.