Adjust oven rack one third up from bottom and preheat to 375 degrees.
Separate the bottom from sides of 9 x 3 inch spring form pan. Butter sides only and replace bottom in pan, set aside.
Crush cookies into fine crumbs (2 cups). Place in mixing bowl, melt butter, and mix together. Pour two thirds of mixture into prepared pan. Tilt pan and press crumbs against sides, leaving top three fourth inch uncrumbed. Pour remaining crumbs and press firmly on bottom.
Melt chocolate and set aside to cool slightly in large bowl. Cream cheese until smooth, add vanilla, salt, and sugar. Beat well, add chocolate and mix. Add eggs one at a time until blended. Add sour cream and beat until smooth.
Pour filling into crust and rotate pan briskly to smooth top.
Bake 1 hour - cake will still seem soft. Let stand on rack until completely cool. Center may fall when cool. Cover with tin foil and refrigerate overnight. Freezes well.