Heat oven to 350 degrees. Line a 9 x 9 x 2-inch pan with nonstick foil.
Crust: In a bowl, combine cookie crumbs, melted butter and sugar. Stir until combined. Press into bottom of prepared pan. Refrigerate while making filling.
Filling: In a saucepan, whisk cornstarch and sugar. Stir in milk and egg. Cook, stirring constantly, over medium heat until smooth, steaming and slightly thickened, about 4 minutes.
In a large bowl, blend pumpkin, brown sugar, pumpkin pie spice and salt. Whisk in milk mixture. Pour over crust; transfer to oven. Bake at 350 degrees for 50 minutes or until center is set. Cool completely on a wire rack; refrigerate until serving. Use foil to lift bar from pan. Slice into squares. Garnish with whipped cream, if desired.