PREHEAT oven to 350° F.
PLACE nuts, brown sugar, flour and butter in food processor container; cover. Process until mixture resembles coarse meal. Press onto bottom of ungreased 10-inch springform pan.
BAKE for 5 minutes. Cool completely in pan on wire rack.
HEAT cream in medium saucepan over medium heat just to boiling. Remove from heat; stir in morsels. Let stand for 5 minutes. Stir until chocolate is melted. Cool for 15 minutes.
BEAT cream cheese and granulated sugar in large mixer bowl on medium speed until smooth. Add chocolate mixture; beat on low speed until just combined. Add eggs; stir until just combined. Pour into prepared crust. Place pan on baking sheet.
BAKE for 55 to 60 minutes minutes or until edge is set but center still moves slightly. Cool in pan on wire rack for 15 minutes; run knife around edge of cheesecake. Cool for 30 minutes. Remove side of springform pan. Cool completely on wire rack. Cover; refrigerate for at least 4 hours or overnight.
FOR CARAMEL SAUCE:
MELT butter in small saucepan. Stir in brown sugar and cream. Bring mixture to a boil. Reduce heat to low; boil, uncovered, for 5 minutes. Cool slightly.
SERVE cheesecake with warm Caramel Sauce and whipped cream.