1. Make the Granola Base: Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, allowing for a 2 inch overhang. Set aside.
2. In a medium mixing bowl, whisk together the flour, oats, baking soda and salt to combine. Add both the granulated sugar and brown sugar and mix until no clumps remain. Stir in the melted butter with a fork until the mixture is evenly moistened. Press half of the mixture into the prepared pan and bake for 15 minutes.
3. Meanwhile make the Pumpkin Pie filling. In a large bowl whisk together the sugars, Pumpkin Pie Spice and salt. Add the egg, egg yolk and vanilla. Whisk until well blended. Finally, whisk in the pumpkin and milk until the mixture is smooth.
4. After the initial 15 minutes of baking, remove the crust from the oven and pour the pumpkin filling evenly over the bottom crust. Smooth the filling edge to edge. Return to the oven and cook for 15 minutes.
5. Remove from the oven, sprinkle the remaining oatmeal crumb mixture over the top of the pumpkin filling. Return the pan to the oven. Bake for an additional 20 to 25 minutes, until golden brown and the center jiggles slightly.
6. Cool completely in the pan. Transfer the pan to the refrigerator to chill for 1-2 hours. Cut into 12 bars. If desired dust with confectioners’ sugar. Bars will keep refrigerated in an airtight contain for 3 days.