In a saucepan over medium heat, warm 1¼ cups (300 g) of the heavy whipping cream until it just begins to simmer.
Pour the hot heavy cream over the chopped chocolate or chocolate chips. Let it sit for 5 minutes, then stir until smooth and fully melted. Allow this mixture to cool to room temperature.
In a separate bowl, whip the remaining 1¼ cups (300 g) of heavy whipping cream to stiff peaks with a hand mixer.
Gently fold the whipped cream into the cooled chocolate mixture until well combined.
Divide the mousse into individual serving dishes and enjoy immediately or refrigerate until ready to serve.
Notes
Let the mixture cool: I always wait until the melted chocolate mixture reaches room temperature before adding the whipped cream so the mousse stays light and airy.Fold gently: I take my time and fold the cream in with slow, gentle motions to keep that fluffy texture intact.