Preheat oven to 200°C. Heat 1 cup milk in a non-stick pan. Add 1 cup caster sugar and stir till it dissolves. Place refined flour in a bowl, add remaining milk and whisk till smooth. Add egg and beat with a hand blender. Add the sweetened milk and whisk well. Pour this mixture into a deep non-stick pan and cook, stirring continuously. Melt butter in the microwave oven and pour into a bowl.
Add 4 egg yolks and whisk. Add cocoa powder and mix well. Add this to the pan and whisk well so that there are no lumps. Cook till thick. Switch off heat and transfer into a bowl to cool to room temperature. You can cool it in a refrigerator. Beat the egg whites with a hand blender till stiff.
Add the remaining caster sugar and beat again. Fold the egg whites into the chocolate custard with a light hand. Grease 4 ramekin moulds and also a bigger bowl. Pour the mixture into them upto ¾ full and bake in the preheated oven for 15-20 minutes. The soufflé in the ramekin moulds will be ready in 15 minutes. The one in the bowl will take 20 minutes. Dredge with icing sugar and serve immediately.