In a medium bowl, combine chilled heavy cream, powdered sugar, and vanilla extract. Beat on medium-high speed until stiff peaks form (about 5 minutes).

In another bowl, beat softened cream cheese until smooth and creamy (about 3 minutes).

Add Nutella and unsweetened cocoa powder to cream cheese. Beat on medium speed until smooth (about 2 minutes).

Gently fold one-third of the whipped cream into the Nutella mixture, then fold in the remaining whipped cream until smooth.

Spoon mousse into serving cups or a piping bag. Refrigerate for 30 minutes if piping.

Optionally, top with extra whipped cream and chocolate shavings or mini chocolate chips before serving.