Preheat the oven to 195'C.
Start by buttering your 6 ramekins: melt the 25g butter and then brush on to the ramekins. Place in the fridge and allow the butter to set. Remove from the fridge and brush with butter for a second time and then dust with caster sugar.
In a bowl, mix together the corn flour, cocoa powder, caster sugar and the egg yolk. Bring the milk to the boil and then add to the cocoa powder mixture. Return to the heat and stir until the mixture starts to thicken. Remove from the heat and allow to cool.
Next, heat the double cream to boiling point. Remove from the heat and add to the chocolate. Stir until all of the chocolate has melted and then set aside and allow to cool.
Once these two chocolate mixtures are cool, mix them together.
Whisk the egg whites and the caster sugar together until you have stiff peaks. Fold through the chocolate mixture. Pour this into the ramekins, transfer to the oven and bake for 14 minutes.
«Do not open the oven whilst the souffles are cooking or they will go flat!»