pre heat oven to 350. lightly grease a 9x13 inch baking pan and lay a piece parchment paper acroos the pan, so it extends the pan slightly. this will make it easy to get bars out of pan.
to make snickerdoodle layer. sift flour,baking powder and salt, set aside. in a large bowl beat, butter, sugar, egg and vanilla until smooth. stir in the flour mixture and mix until well blended.spread evenly in prpared pan. mixture will be thick and cookie batterish.
to make pumpkin pie filling. in a mixer bowl, beat sugar and butter. add the rest of the filling ingredients and mix until well blended. pour over the snickerdoodle layer, smoothing out the top.
the topping layer; combine the sugar and cinnamon in a small bowl. evenly sprinkle over top of filling.
bake for 33-40 minutes. do toothpick test, if it comes out clean it is done. let bars cool completely, about an hour. they will deflate a bit and remain a bit pie like on the top layer.
after bars are cooled, place the chocolate into a bowl and melt on low power, when completely melted add pumpkin pie spice and mix. use a spoon to drizzle over top of bars and let harden. use parchment paper to lift bars out of pan, place on cutting board and cut into bars.