In a medium bowl, combine flour & sugars. Cut in butter until the mixture resembles course crumbs. Press into 13x9x2" baking pan. Bake at 350° for 18-20 minutes or until lightly browned.
Meanwhile, in a mixing bowl, beat cream cheese and brown sugar until smooth. Add eggs and extract. Beat on low speed until combined. Stir in half chocolate chips, butterscotch chips and walnuts. Spread over crust. Sprinkle with the remaining chocolate chips.
Bake at 350° for 20-25 minutes or until center is almost set. Cool completely on wire rack before cutting.