At least 4 to 5 hours before serving time, combine ice cream and 1 1/2 cups pumpkin puree in a large mixing bowl; stir until well blended. Freeze mixture 2 hours.

Beat with an electric mixer or in a food processor until smooth. Tightly cover; freeze for 2 hours, or until mixture is firm.

At serving time, in a 4 - quart punch bowl or pitcher, gently stir together remaining 1 cup pumpkin puree, apple cider and seltzer.

Scoop frozen pumpkin ice cream mixture into balls; add to punch. Serve immediately.