1. If using cooked fresh pumpkin puree, add to a blender with 1 cup of the smoothie drink; cover and blend until smooth.
2. In a 5- to 6-quart saucepan combine remaining smoothie drink, the blended pumpkin mixture or canned pumpkin, and pumpkin pie spice; heat about 10 minutes until warm.
3. Add about three-quarters of the ice cream by spoonfuls. Heat and stir 3 to 5 minutes more, until just melted. Pour into a punch bowl. Top with scoops of remaining ice cream. Serve immediately (nog will be slightly warm).