Heat 0.25 cup of heavy cream in a microwave-safe bowl for about 50 seconds until warm.

Add the chocolate chips to the warm cream and stir until completely melted. Allow to cool slightly.

Pour the remaining 0.25 cup of heavy cream into a mixing bowl and beat with a hand-held or stand mixer until soft peaks form, then continue until stiff peaks form.

Gently fold half of the whipped cream into the cooled chocolate mixture. Repeat with the remaining whipped cream until fully incorporated.

Divide the mousse into 4 serving glasses or ramekins. Refrigerate for at least 1 hour before serving.

Serve chilled, optionally topped with additional whipped cream or chocolate shavings.