Preheat the oven at 160 C.
Mix the corn flour with the milk and bring to a boil.
Add the chocolate and mix until it's melted. Remove from the stove.
Add the egg yolk and mix well.
Grease the ramekins with butter and dust with sugar.
Whisk the egg whites until they can hold their shape. Pour the chocolate mix and whisk gently until completely incorporated.
Pour the mix into the ramekins.
Bake for 20 min, until risen and set on top. Mine has risen one third, but then collapsed after it has been removed from the oven.
