Chocolate Caramel Cheesecake

• Make crumb crust as directed in separate recipe, using chocolate wafer cookies instead of graham crackers.
• Preheat oven to 350°F.
• Cook sugar in a dry heavy saucepan over moderately low heat, stirring slowly with a fork, until melted and pale golden. Cook caramel without stirring, swirling pan, until deep golden. Remove from heat and carefully add heavy cream (mixture will vigorously steam and caramel will harden). 
• Cook over moderately low heat, stirring, until caramel is dissolved. Remove from heat and whisk in chocolate until smooth. Stir in sour cream.
• Beat cream cheese with an electric mixer until fluffy, then beat in chocolate mixture on low speed. 
• Beat in eggs, 1 at a time, then vanilla, beating on low speed until each ingredient is incorporated and scraping down bowl between additions.
• Put springform pan with crust in a shallow baking pan. Pour filling into crust and bake in baking pan (to catch drips) in middle of oven 55 minutes, or until cake is set 3 inches from edge but center is still slightly wobbly when pan is gently shaken.
• Run a knife around top edge of cake to loosen and cool completely in spring form pan on a rack. (Cake will continue to set as it cools.) 
• Chill cake, loosely covered, at least 6 hours. Remove side of pan and transfer cake to a plate. 
• Bring to room temperature before serving.

• Stir together crust ingredients and press onto bottom and 1 inch up side of a buttered 24-centimeter springform pan.
•  Fill right away or chill up to 2 hours.