Heat the oven at 180 degrees.Grease the tray with butter and place a baking paper.
Melt chocolate and butter at “Bain Marie”,then mix cocoa powder and sugar.
In the bowl removed from “Bain Marie” add cocoa powder and sugar.
Mix vanilla essence,eggs one by one in the chocolate composition.
Mix flour and salt in chocolate composition.
Put the composition in the tray and bake for 20-30 minutes.