Step 1: In a large bowl, use an electric mixer to beat the room temperature cream cheese until completely smooth and creamy. Add the powdered sugar, creamy peanut butter, vanilla extract, and salt. Mix on low speed to combine, then increase to medium-high and beat for 2-3 minutes until light and fluffy, scraping down the sides of the bowl as needed. Set aside.

Step 2: In a separate, chilled bowl with clean beaters, whip the very cold heavy cream on medium-high speed. Continue whipping until stiff peaks form (the peak holds its shape when the beaters are lifted). Be careful not to over-whip.

Step 3: Add about one-third of the whipped cream to the peanut butter base and stir gently with a spatula to lighten the mixture. Add the remaining whipped cream and use a folding motion (cutting down the center, scraping the bottom, and lifting up and over) until no white streaks remain. Do not overmix.

Step 4: Spoon or pipe the mousse into serving dishes. Cover and refrigerate for at least 4 hours, or overnight, to allow the mousse to set firmly and the flavors to meld.