Mix together the pumpkin and vanilla. Set aside.
In a bowl, mix together the egg yolks, 1/2 cup of heavy cream, cinnamon, ginger, and nutmeg. Set aside
In a cold kettle, whisk together 1 1/2 cups of cream, brown sugar, and molasses.
Turn the heat on to medium high. Continue whisking for 5 minutes, never allowing the cream to boil.
Slowly pour in the hot cream mixture into the egg mixture. Whisk well.
Pour the mixture back into the kettle. Continue whisking for 5 minutes.
Pour the mixture into the pumpkin. Mix thoroughly.
Place the bowl into another larger bowl filled with ice water. Let the mixture cool for 30 minutes. Placd the mixture into the refrigerator and let cool furthermore for 2 hours.
Pour the mixture into your ice cream machine and use according to the manufacturer’s instructions.
Churn the ice cream for 25 minutes.
Pur the ice cream into a graham cracker pie crust. Cover and let firm up for 6 hours.
Top with whipped cream.