In a saucepan over low heat, combine your large marshmallows, pure pumpkin, cinnamon, pumpkin pie spice, and a pinch of salt. Stir frequently for about 5-7 minutes, until melted.

Transfer the melted mixture into a large mixing bowl and allow it to cool to room temperature for about 30 minutes.

Once cooled, gently fold in the thawed Cool Whip using a rubber spatula.

Carefully pour the fluffy filling into the prepared graham cracker crust.

Cover with plastic wrap and refrigerate for at least 8 hours, preferably overnight.

Once chilled, slice and serve, optionally topping with additional whipped cream.