Line the Molds
Coat the bottoms and sides of six 6-ounce individual soufflé molds with butter.
Divide the sugar evenly among the molds, and then tilt and rotate the molds to coat the bottoms and sides fully and evenly. Refrigerate the molds while you prepare the soufflé base.
Prepare the Orange
Using a very sharp knife, carefully slice the orange into 1/4 inch slices.
Gently stir the oranges, sugar and water in a large saucepan to coat. Scrape the vanilla seeds from the bean into the pan.
Place over medium heat and bring to a boil, stirring to dissolve the sugar.
Adjust the heat to maintain a simmer and cook for 15 minutes.
Remove from heat and let the mixture cool completely at room temperature. Once cool, chop the mixture into fine pieces. You will need about ½ cup of chopped orange for the base.
Bake the Soufflés
Preheat the oven to 350°F.
Combine the flour and sugar in a medium bowl and whisk together by hand.
Place the egg yolks in a medium bowl and whisk by hand until blended.
Put the milk in a medium saucepan and bring to a boil over medium heat. Reduce the heat and add the flour mixture. Whisk until the mixture is smooth.
Remove from the heat. Whisk 2 tablespoons of the milk-flour mixture into the egg yolks to warm them slightly.
Carefully add the yolks to the remaining milk-flour mixture.
Place over medium heat and cook, whisking constantly, until the base is the consistency of mayonnaise, 4 to 5 minutes. Remove from the heat. Transfer the base to a large bowl and cover with plastic wrap to prevent a skin from forming. Let cool for 30 minutes.
Put the egg whites in the bowl of a stand mixer fitted with the whip attachment. Beat on medium speed until they start to froth. Increase the speed to high and add the sugar. Beat until the whites start to lose their shine but still look wet. They hill hang in medium-stiff peaks when the whip is lifted from the bowl.
Fold about one-third of the whites into the base with a rubber spatula. Gently fold in the rest of the whites, chopped chocolate and orange filling just until no streaks remain.
Distribute the mixture evenly among the prepared molds, filling them level and smooth with the top. Put the molds on a sheet pan.
Bake on the middle shelf of the oven until the soufflés rise about 1 inch above the rim of the molds and have a crust on top, about 20 minutes. They will be wobbly.
Transfer them to serving plates and take them to the table immediately.
Variation
Just before serving, pierce the cap of each soufflé and spoon a tablespoon of Extra-Bitter Chocolate Sauce mixed with a touch of Grand Marnier into the center.
