4tsps.Sugar plus 2 tsp. for egg white and a bit more for dusting the inside of the oranges
Pre-heat oven to 400
Prepare a baking sheet lined with parchment
Cut the tops off the oranges and remove the flesh by cutting around the edge straight down and then removing with a grapefruit spoon. Strain out the pulp and pits and set the juice aside. After removing the flesh from the peel cut just enough off the bottoms of the oranges to create a flat surface.
In a small saucepan whisk together egg yolks, sugar, and cornstarch until smooth. Whisk in half of the reserved juice and heat, stirring constantly, over a medium heat until thickened. Remove from heat and stir in the zest and dark rum. In a medium bowl whisk egg white until it begins to get fluffy then add sugar and whisk to soft peaks. Melt the chocolate with 1 tsp. of the reserved juice. Fold the egg whites into the orange cream until completely incorporated then add the chocolate orange mixture and fold in a couple of times to evenly distribute the chocolate but leave it in swirls.
Fill the orange peels with the soufflé mixture, flattening the tops if desired (this gives them a neater appearance and makes them less likely to topple).
Bake for 18-20 minutes until risen and golden brown on top.
Serve immediately sprinkled with powdered sugar and drizzled with a bit of the reserved juice.