Preheat the oven to 350F degrees and position the oven rack in the middle of the oven.
LIne a 9x13 inch pan with parchment paper, leaving an overhang around the edges.
In a medium bowl whisk together the flour, powdered sugar, cornstarch and salt.
Stir in the melted butter and egg.
Press the mixture into the bottom of the prepared pan.
Bake for 10 minutes, and remove from the oven (keep the oven turned on).
Pumpkin Pie Filling
In a large bowl whisk together the brown sugar, pumpkin pie spice and cornstarch to remove any lumps from the brown sugar.
Whisk in the pumpkin pie filling, evaporated milk and eggs until smooth.
Pour the filling over the base.
Bake in the preheated oven for 40-50 minutes, or until the middle no longer wobbles and an inserted toothpick comes out clean or with a few damp crumbs.
Remove from the oven and cool completely, then cover and place in the fridge for 4 hours to set.
15 oz can of evaporated milk can be substituted for 1 1/2 cups heavy cream. Do not substitute evaporated milk with milk.To make your own pumpkin pie spice, use 1 1/2 teaspoons cinnamon, 1/2 teaspoon ginger powder, 1/2 teaspoon ground nutmeg, and 1/8 teaspoon ground cloves.Storage & Make Ahead Tips:Store bars in an airtight container in the fridge for up to 4 days. Bars can be frozen for up to 3 months in an airtight container, then thaw in the fridge. Ensure bars are fully cooled before freezing.