Preheat oven to 325 degrees. Spray a 9" square baking pan with cooking spray, then line it with parchment paper and set aside.Prepare the Crust: Start by crushing the graham crackers until the are fine.In a small bowl, combine cracker crumbs and sugar; add butter and stir until moistened. Press mixture into the prepared baking pan. Bake for 7 to 10 minutes or until set. Move to a wire rack to cool completely.Now work on the filling: In a large bowl, beat cream cheese, sour cream, sugar, flour and vanilla until smooth in texture. Add the lightly beaten egg, andbeat on low until just combined.Now Pour 3/4 cup batter into a small bowl. Add pumpkin, brown sugar and cinnamon, stirring until well blended.Next pour the plain batter over cooled crust. Now add the next layer of pumpkin batter over the plain batter.Finally bake it at 325 degrees for 20 to 25 minutes or until center is almost set. Cool on wire rack for 1 hour. Cover and refrigerate at least 2 hours to overnight before serving it.