Chill mixing bowl and whisk attachment in the freezer for about 10 minutes
Pour cold heavy whipping cream into chilled bowl and begin whipping on medium speed
Once cream starts to thicken slightly, add keto sweetener and continue whipping
Whip until soft peaks form and set aside
In separate bowl, beat softened cream cheese until smooth and creamy
Add fresh lime juice, lime zest, vanilla extract, and a pinch of salt into the cream cheese
Mix until fully incorporated and smooth
Gently fold whipped cream into cream cheese mixture in batches
Continue folding until completely combined and airy
Taste and adjust sweetener or lime to preference
Spoon mousse into individual serving cups or ramekins
Refrigerate for at least 30 minutes to allow mousse to set
Serve chilled for best flavor and texture