In a medium bowl, mix cream cheese and peanut butter with a hand mixer until smooth.
In a separate bowl, combine heavy cream, sweetener, and vanilla. Mix with a hand mixer until thickened and stiff peaks form.
Add half of the whipped cream to the cream cheese mixture and mix with a hand mixer. Add the remaining whipped cream and gently fold it in with a spatula.
Refrigerate 1 hour before serving. Garnish with additional whipped cream and chopped peanuts if desired.
Notes
Allow peanut butter and cream cheese to come to room temperature for the easiest blending.
Peanut butter mousse can be chilled in individual dessert cups for an easy make ahead snack or dessert for low carb guests.