Preheat oven to 350°.
Place first 3 ingredients in a bowl; beat at medium speed of a mixer until blended. Add crumbs; stir well. Firmly press mixture into bottom and 1 inch up sides of an 8-inch springform pan coated with cooking spray. Bake at 350° for 10 minutes; let cool on a wire rack.
Combine rum and chocolate squares in the top of a double boiler. Cook over simmering water 2 minutes or until chocolate melts, stirring frequently. Remove from heat; add chocolate syrup, stirring until smooth.
Preheat oven to 300°. Place cheeses in a large bowl; beat at medium speed of a mixer until smooth. Add 1 cup sugar, 2 tablespoons cocoa, vanilla, and salt; beat until smooth. Add rum mixture; beat at low speed until well-blended. Add eggs, 1 at a time, beating well after each addition.
Pour cheese mixture into prepared pan; bake at 300° for 40 minutes or until almost set. Combine sour cream, 1 tablespoon sugar, and 2 teaspoons cocoa; stir well. Turn oven off, and spread sour cream mixture over cheesecake. Let cheesecake stand for 45 minutes in oven with door closed. Remove cheesecake from oven, and let cool to room temperature. Cover and chill at least 8 hours. Garnish with chocolate curls, if desired.