Add the heavy cream, powdered sugar and vanilla extract to a mixing bowl fitted with a whisk attachment. Combine the ingredients on low for 1 minute, then increase the speed of the mixer to medium speed.
Mix for about 4 - 5 more minutes or until the cream has whipped to medium stiff peaks. Transfer the whipped cream to another bowl and set aside for now.
Add the cream cheese to the cleaned out bowl used to make the whipped cream. Using the paddle attachment mix the cream cheese with light brown sugar, vanilla extract and pumpkin spice until smooth and well combined.
Add about ¾ of the whipped cream into the pumpkin cream cheese mixture. Reserve the remaining whipped cream to top the mousse before serving. Gently hold the whipped cream into the pumpkin filling using a large flexible silicone spatula or spoon.
Transfer the pumpkin mousse filling into dessert cups. Top the mousse with the reserved whipped cream. Transfer the pumpkin dessert to the fridge to set for at least 1 - 2 hours.