Pre heat the oven to 160 fan oven 350 farenheit
Line the whole tray with baking paper - leaving the paper to stand quite tall at the sides for lifting the brownies out of the tray.
Melt the butter and stand to one side to cool slightly
Place the sugars in the bowl. Smoothing out any big lumps of dark brown sugar.
Add the plain flour and cocoa powder to the sugar mix
Add in 3 eggs, vanilla extract and the melted butter and stir with a wooden spoon to combine the mixture together.
Add in the chocolate chips or chunks
Pour in the prepared tin and bake for 25 minutes
Leave to cool for 5 minutes or slightly set and then lift the brownies with the paper out of the tin.
Decorate with eggs and slice as desired.