Place a greased 9-in. springform pan on a double thickness of heavy-duty foil (about 18 in. square). Securely wrap foil around pan. In a small bowl, combine cracker crumbs and brown sugar; stir in butter.
Press onto the bottom and 1 in. up the sides of prepared pan. Place pan on a baking sheet. Bake at 350° for 10 minutes. Cool on a wire rack.
In a large bowl, beat cream cheese until smooth. Beat in the chocolate, brown sugar and cocoa. Add eggs; beat on low speed just until combined. Stir in extracts. Pour into crust.
Place pan in a large baking pan. Fill larger pan with 1 in. water. Bake at 350° for 50-55 minutes or until center is just set and top appears dull. Remove springform pan from water bath. Cool on a wire rack for 10 minutes. Carefully run a knife around edge of pan to loosen; cool 1 hour longer. Refrigerate for 4 hours or overnight. Remove sides of pan.
In a large saucepan, combine topping ingredients. Bring to a boil over medium heat; cook and stir for 3 minutes. Cool. Spread topping over cheese cake. Refrigerate leftovers. Yield: 12 servings.