Dutch Chocolate-Mint Cheesecake - chocolate wafer

Method

• Finely grind cookies, chocolate and sugar in processor.
• Add butter; blend until crumbs begin to stick together.
• Press crumb mixture firmly onto bottom and up sides of 9-inch-diameter springform pan with 2 3/4-inch-high sides.
• Position rack in center of oven and preheat to 350F.
• Melt chocolate in top of double boiler over simmering water, stirring until smooth.
• Cool to lukewarm.
• Using electric mixer, beat cream cheese and sugar in large bowl until blended.
• Add eggs 1 at time, beating just until incorporated.
• Add melted chocolate, cream, cocoa powder and extracts and beat just until smooth.
• Pour filling into crust.
• Bake until center is just set, about 1 hour.
• Transfer to rack and cool 20 minutes.
• Press down gently on puffed edges to flatten.
• Run small sharp knife around top edge of pan to loosen.
• Do not remove pan sides.
• Cool.
• Cover and chill overnight.
• Preheat oven to 350F.
• Combine sour cream and sugar in bowl.
• Spoon sour cream topping over cheesecake.
• Bake 20 minutes.
• Chill cheesecake until cold, at least 6 hours.
• Bring cream and butter to simmer in heavy small saucepan.
• Reduce heat to low.
• Add chocolate and whisk until melted.
• Freeze until firm enough to pipe, whisking occasionally, about 15 minutes.
• Remove pan sides from cake.
• Spoon chocolate topping into pastry bag fitted with small star tip.
• Pipe 6 diagonal lines atop cake, spacing evenly.
• Repeat in opposite direction, forming lattice.
• Pipe 12 rosettes of chocolate around top edge of cake.
• (Can be made 1 day ahead; chill.)
• Garnish with mint leaves.