Preheat oven to 350 degrees. Add enough water to fill a medium saucepan 1/2 inch. Heat to simmer.
In a large, heat safe bowl, add chocolate and butter. Place over saucepan of water. Do not let the bottom of the bowl touch the water directly. Cook, whisking often until the chocolate and butter are melted. Remove the bowl from the saucepan then whisk in sugar and salt.
Whisk in egg yolks, vanilla and flour until just combined then pour into graham cracker crust. Place in oven and bake for 20 minutes or until just set.
In a medium-sized bowl, whisk pumpkin, heavy cream, egg, vanilla, sugar, flour, pumpkin pie spice and salt. Whisk until smooth. Pour over brownie layer then place back in oven for 12-15 minutes or until set. A slight jiggle is ok.
Place foil or a pie crust shield around the edge of the crust during baking if needed to prevent over-browning.
Let pie cool for 20-30 minutes on a cooling rack then place in refrigerator to chill for 1-2 hours before serving.
Add whipped cream to individual servings.