Combine the first three ingredients; press onto the bottom and 1-1/2 in up the sides of a greased 10-in. springform pan. Bake at 350° for 10 minutes; cool completely.
In a large bowl, beat the cream cheese, sugar and sour cream until smooth. Add eggs; beat on low speed just until combined. Stir in chocolate. Pour into crust. Place pan on a baking sheet
Bake at 350° for 1 to 1-1/4 hours or until center is nearly set. Cool to room temperature, about 2 hours.
Combine the sour cream, sugar and extract; spread over filling. Bake at 450° for 5-7 minutes or until set. Chill, uncovered, 1 hour. Arrange oranges on cheesecake. Cover and refrigerate at least 4 hours. Refrigerate leftovers.