6 oz (1 cup) semi-sweet chocolate
Chips
1 c  Flour
2 tb + 1 cup sugar
1/4 ts Salt
1/4 c  Butter
3    (8-oz) pkgs cream cheese
2 ts Vanilla
1 c  Dairy sour cream
6    Eggs, separated

Melt chocolate morsels in top of double boiler over hot water.
Combine 3/4 cup flour, 2 Tbls. sugar & salt. Cut in butter until
particles are fine. Stir in 2 Tbls. chocolate. Press into bottom of
nine-inch spring-form pan. Bake 400x for ten minutes. Soften cream
cheese with 1 cup sugar in mixing bowl. Blend in 1/4 cup flour &
vanilla. Add egg yolks; beat well. Blend in sour cream. Beat egg
whites until soft peaks form. Fold into cheese mixture very
thoroughly. Combine remaining chocolate with 1 3/4 cup cheese
mixture. Pour half of plain mixture over baked crust. Top with
spoonfuls of half of chocolate mixture. Cover with remaining plain
mixture, then with chocolate mixture. Cut through batter with spatula
to marble. Place in 400 oven. Immediately set at 300. Bake one hour.
Turn off oven; let remain in closed oven one hour. Cool away from
drafts two to three hours. Chill at least eight hours before serving.
To cut, use wet hot sharp knife.