1 1/2 tablespoons unsalted butter, plus extra for the ramekins
2 teaspoons icing sugar, plus extra for decorating
170 g dark chocolate, roughly chopped
2 tablespoons milk
4 egg whites
1/4 cup caster sugar
3 egg yolks
1/2 teaspoon vanilla extract
Preheat the oven to 190ºC. Butter the insides of 4 ramekins (small round ovenproof dishes) and dust each with ½ teaspoon of icing sugar. Rotate the ramekins so the sugar evenly coats them.
Bring a few centimetres of water to a boil in a saucepan. Set a heatproof bowl over the saucepan, making sure the bottom does not touch the water. Place the butter and the chocolate in the bowl to melt, stirring occasionally to incorporate. As the chocolate begins to melt, add the milk and continue to stir. Keep a careful eye on the mixture—you don’t want to overcook it. As soon as it becomes smooth, take it off the heat. Let cool for 5 minutes.
Meanwhile, in a large bowl, whisk the egg whites with a hand mixer until soft peaks form (when you pull the whisk out, the mixture should fold over on itself, not stand up straight). While whisking, gradually add the caster sugar in three parts, making sure each addition has been incorporated before adding the next. Whisk until the egg whites are glossy and stiff peaks form (when you pull the whisk out, the mixture should be left standing tall like the peaks on a mountain).
Back to the chocolate sauce: Using a metal spoon, add one egg yolk at a time and stir until completely mixed in before adding the next. Stir in the vanilla extract.
Here is the tricky bit: The egg white mixture is full of air, and the more you mix it, the more air is lost. Air is important for the soufflé to rise in the oven. Pour the chocolate sauce into the egg whites, and using a flat spatula, fold the mixture gently from the outside in. Do not stir through the centre. Continue to gently fold until completely mixed. Then, spoon the mixture evenly among the prepared ramekins. Remember, the mixture will rise, so do not fill the dishes up all the way. Set the ramekins on a baking tray, carefully transfer to the oven, and bake for 8 minutes.
Immediately dust the soufflés with icing sugar, and serve hot.