Add the Nutella to a large mixing bowl and set aside.
In a separate microwave-safe bowl, add 0.25 cup of the heavy whipping cream. Heat in the microwave for 45 to 60 seconds until hot and starting to bubble.
Carefully pour the hot cream over the Nutella. Let sit for 1 minute to soften, then stir until smooth and combined. Let cool to room temperature.
Pour the remaining heavy whipping cream into a mixing bowl. Using a handheld mixer, whip on low to high speed until stiff peaks form, about 3 to 5 minutes.
Gently fold one-third of the whipped cream into the cooled Nutella mixture. Repeat with the next third and then the remaining whipped cream, being careful not to deflate the mousse.
Spoon the mousse into serving dishes and refrigerate for at least 2 hours before serving.
Top with additional whipped cream if desired and serve chilled.
Notes
This mousse keeps well in the refrigerator for up to 3 days. Garnish with fresh berries or a sprinkle of chopped hazelnuts for extra texture and flavor.