Position an oven rack in the 3rd part of an oven. Heat to 325°. Line the bottom and side of an 8 inch square baking pan with aluminium foil, leaving an over hang on 2 opposite sides.

Add enough water to a medium sauce pan, so that it is 1 to 2 inches deep, heat water until simmering. Combine butter, sugar, cocoa powder and the salt in a medium heat safe bowl.

Rest the bowl over simmering water. Stir mixture occasionally until the butter has melted and mixture is quite warm. Don't worry if it looks gritty. It will become smooth once you add the egg and flour.

Remove the bowl from heat and set aside for 3 -5 mins until it is only warm not hot.

Stir in vanilla with a wooden spoon, then add eggs one at a time and stir very well.

When the batter looks thick and well blended add the flour and stir very well then beat with the wooden stick for 40 to 50 strokes. Beat very well.

Bake 20 to 25mins, until a toothpick can be inserted in the center and it will come out clean.

Cool completely then remove from pan. For coolest line when cutting place in freezer for 20 -30mins to firm up. It is ready to enjoy with coffee or tea.