Preheat the oven to 325°F.
Melt the butter and set aside to cool.
Sift together the flour and cocoa powder.
In a large bowl, beat the eggs and sugar for 5-10 minutes until pale yellow.
Slowly add the dry ingredients to the egg mixture just until combined.
Pour the melted butter into a baking dish.
Place the baking dish in a larger pan and pour hot tap water into the larger pan, halfway up the sides of the baking dish.
Bake for exactly 1 hour.
