Preheat the oven to 350 degrees Cut the top of the pumpkin and scoop out the seeds Put the top back on the pumpkin and into the oven for 1 hour or until fork tender. Scrape out 3 cups of pumpkin pulp and add to a food processor.
Add the sugar, allspice, nutmeg, rum and vanilla. Puree to combine. In a large bowl, whip the cream until it has a very stiff texture. Fold in the pumpkin mixture. Pour into 4 ounce dessert glasses and chill for 2 hours until set.