Cut the tops off the 6 oranges. Scoop out the flesh from each orange, leaving just the peel intact. Be careful not to puncture the peel. Carve little faces into each orange - get creative here!

In a microwave-safe bowl or using a double boiler, melt the dark chocolate and butter together until smooth. Stir in the orange zest and set aside to cool.

Whisk the egg yolks directly into the melted chocolate mixture until well combined.

In a clean, dry bowl, whip the egg whites with ¼ cup of sugar until stiff peaks form, creating a meringue.

Gently fold the whipped egg white meringue into the chocolate mixture until well combined.

In a separate bowl, whip the 35% cream with 2 tablespoons of sugar until it reaches soft peaks.

Carefully fold the whipped cream into the chocolate mousse mixture until no streaks remain, creating a smooth and airy mousse.

Using a spoon, carefully fill each hollowed-out orange peel with the chocolate orange mousse mixture. You can also pipe the mixture into each orange with a large piping tip such as a Wilton 4B.

Place the filled orange jack-o-lanterns and their lids in the refrigerator for at least 2 hours, or until the mousse is set.