In a microwave-safe bowl, heat half a cup of the heavy cream for about 50 seconds, depending on your microwave’s strength.

Add the chocolate chips to the warm cream and stir until the chocolate is completely melted and the mixture is smooth. This should take about 1 to 2 minutes. Set it aside to cool to room temperature.

Pour the remaining heavy cream into a medium mixing bowl. Using a hand mixer or a stand mixer fitted with the whisk attachment, beat the cream until soft peaks form. Continue whipping until stiff peaks form.

Using a large spatula, gently fold half of the whipped cream into the cooled chocolate mixture. Once mostly combined, carefully fold in the remaining whipped cream until no streaks remain.

Divide the mousse evenly between four ramekins, small bowls, or cocktail glasses. Refrigerate for at least one hour, or up to overnight, to set.

When ready to serve, top with extra whipped cream or Cool Whip and sprinkle with chocolate shavings, if desired.