Emulsify melted butter with milk and melted cocoa mass together.
In a mixing bowl with whisk attachment, prepare a Sabayon with egg yolk, whole egg, sugar and inverted sugar together.
Fold in soft peak meringue, followed by, flour, cocoa powder, salt and ganache mixture.
Bake at 160c, Fan Speed 3, Vent Out (Steam), 15 minutes.