Chop the dark chocolate into small pieces and place them in a microwave-safe bowl.

Heat the chocolate in 15-second intervals, stirring until smooth and melted. Allow it to cool to room temperature.

In another bowl, pour the chilled heavy cream and begin whipping it on low speed, gradually increasing to medium-high until soft peaks form.

Gently whisk in the fresh orange juice and zest into the cooled chocolate.

Carefully fold one-third of the whipped cream into the chocolate mixture, then delicately incorporate the remaining whipped cream.

Prepare a springform pan by lining the bottom with parchment paper and pour in the mousse, smoothing the top with a spatula.

Refrigerate the mousse for a minimum of 2 hours before serving.