In a medium mixing bowl, whisk well the pumpkin, 1/4 cup of the granulated sugar, cornstarch, salt, egg yolks, vanilla and pumpkin spice. In a medium saucepan, heat the milk on medium until it is hot but not scalding. Slowly, while whisking, drizzle 2/3 of the hot milk into the pumpkin mixture, then pour the pumpkin mixture into the saucepan with the remaining milk and heat to 165 degrees, stirring constantly. Immediately pour the custard into a large bowl and cover with plastic, letting the plastic lay directly on top of the custard. Cool to room temperature by chilling it in the fridge for a half hour. Don't let it get completely cold yet.
Make the meringue.
Pour the 1/2 cup of sugar in a small sauce pan with 1/4 cup of water. Whisk the egg whites in the bowl of a stand mixer until foamy then add the cream of tartar. Continue to whisk on medium-high until they just reach soft peaks, which will take about 4 minutes.While the egg whites are whisking. Heat the sugar and water on medium-high. Stir it until the sugar dissolves then leave it alone with a candy thermometer. Heat the syrup until it reaches 240 degrees. Ideally, you want to the syrup to reach temp at the same time the whites reach soft peaks, but this doesn't always happen. If soft peaks are reached first, turn the mixer off until the syrup is the right temperature.Once the syrup has reached 240 degrees, and the whites have reached soft peaks, drizzle the syrup into the egg whites with the mixer running on medium speed. Once it is all in, turn the mixer to high and let it continue whisking for 8 minutes. Fold the meringue gently into the cooled pumpkin custard.
Make the whipped cream cheese.
Beat the softened cream cheese with a paddle attachment for 3 minutes until creamy. Scrape down the sides of the bowl with a rubber spatula. Switch to a whisk attachment. Add the heavy cream. Whisk on medium- high for 4 minutes.Fold the whipped cream cheese into the pumpkin/meringue mixture. Cover with plastic. Place the mousse into the refrigerator for at least 2 hours to set. Spoon or pipe into cups. Serve with chopped, candied nuts, crushed pretzels, caramel sauce or more whipped cream.