Your pumpkin pie recipe is missing one key ingredient: the crust. Why not cook a whole pie, then let it cool. Take most of the innards of the pie (not the crust) and mix in extra cream to turn it all into an ice cream base. save the crust. Make ice cream out of the innards+cream, then at the last minute crumble the crust into bite sized bits and stir in crust with one or two swirls. Or, to make it easier, just dump the whole pie with crust into a bowl, add extra cream to turn it into an "ice cream" then mix and freeze it all together.