In a saucepan over low heat, combine the large marshmallows, pure pumpkin, cinnamon, pumpkin pie spice, and a pinch of salt. Stir continuously for about 5–7 minutes, until the marshmallows have melted and the mixture is smooth.

Transfer the filling to a mixing bowl and allow it to cool to room temperature for about 30 minutes, stirring occasionally.

After cooling, gently fold in the thawed Cool Whip with a spatula until thoroughly combined.

Pour the pumpkin and marshmallow mixture into the graham cracker crust, spreading it evenly.

Cover the pie and refrigerate for at least 8 hours, preferably overnight.

When ready to serve, take the pie out of the refrigerator, top with additional whipped cream if desired, and slice into wedges.