Heat ½ cup of heavy cream in a saucepan until warm but not boiling.
Pour the warm cream over the chocolate chips and let sit for 2 minutes.
Stir until smooth and fully melted, then allow the mixture to cool slightly.
In a separate bowl, whip the remaining 1 cup heavy cream with powdered sugar until stiff peaks form.
Gently fold the whipped cream into the cooled chocolate mixture until fully combined and fluffy.
Spoon the mousse into serving glasses and refrigerate for at least 1–2 hours before serving.
