Ingredients

• 24 chocolate wafer cookies (from one 9-ounce package)
• 1 tablespoon sugar
• 1/4 cup (1/2 stick) butter, melted
• 1 9.7-ounce bar Scharffen Berger 70% Cocoa Bittersweet Chocolate,* chopped
• 4 (8-ounce) packages cream cheese, room temperature
• 1 1/4 cups plus 2 tablespoons sugar
• 1/4 cup unsweetened cocoa powder (preferably Scharffen Berger)
• 4 large eggs
• 3/4 cup whipping cream
• 6 ounces Scharffen Berger 70% Cocoa Bittersweet Chocolate,* chopped
• 1 tablespoon sugar
• Bittersweet chocolate curls
• *If unavailable, substitute another high-quality bittersweet chocolate.

Instructions

1. Preheat oven to 350°F. Butter 9-inch-diameter springform pan with 3-inch-high sides. Blend cookies in processor until finely ground; blend in sugar. Add melted butter and process until well blended. Press crumbs evenly onto bottom (not sides) of prepared pan. Bake just until set, about 5 minutes. Cool while preparing filling. Maintain oven temperature.
2. Stir chopped chocolate in metal bowl set over saucepan of simmering water until melted and smooth. Remove bowl from over water; cool chocolate until lukewarm but still pourable. Blend cream cheese, sugar, and cocoa powder in processor until smooth. Blend in eggs 1 at a time. Mix in lukewarm chocolate. Pour filling over crust; smooth top. Bake until center is just set and just appears dry, about 1 hour. Cool 5 minutes. Run knife around sides of cake to loosen. Chill overnight.
3. Stir cream, 6 ounces chocolate, and sugar in heavy medium saucepan over low heat until smooth. Cool slightly. Pour over center of cheesecake, spreading to within 1/2 inch of edge and filling any cracks. Chill until topping is set, about 1 hour. Do ahead: Can be made 3 days ahead. Cover with foil and keep refrigerated.
4. Release pan sides. Transfer cheesecake to platter. Top with chocolate curls. Let stand 2 hours at room temperature before serving.