In a large mixing bowl (or the bowl of a stand mixer fitted with the paddle attachment), combine the peanut butter, powdered sugar, and vanilla extract.
Slowly add the milk to the peanut butter mixture, stirring constantly. Continue mixing until well combined and no lumps remain.
Gently fold in the whipped topping. Be careful not to overmix– we want the mousse to stay light and fluffy!
Transfer to your serving dishes and enjoy immediately or refrigerate until ready to use. This peanut butter mousse can be made up to 12 hours in advance.
This nutrition information is based on the exact products I used in this recipe. Brands and sizes of products could alter exact nutrition and should always be calculated independently.