Preheat the oven to 160 degrees C. Line a baking tin with a piece of foil or baking paper.
In a medium size microwave safe bowl heat the butter and chocolate on high for 1 minute. Remove and stir until blended. You may need a further 30 seconds. Stir until smooth. Cool slightly so that you do not cook the eggs when you add them.
In another bowl whisk the sugar with the eggs using a whisk until light and creamy.
Add the melted chocolate to the whisked eggs then add the vanilla essence and mix thoroughly with a wooden spoon.
Sift in the flour and cocoa powder then mix well.
Using a spatula scrape the chocolate mixture into the prepared baking tin.
Put the tin in the oven and cook for 20-25 minutes. Check the brownies by pushing in a cocktail stick or knife in the middle of the mix and when pulled out you should see some of the mix still sticking to the stick or knife. Don’t overcook as it becomes very dry.
Take the brownies out of the oven and let the tin stand on a cake rack until it has cooled down. Once cool take the brownies out and cut into squares and decorate.