Heat oven to 180oC/350oF/Gas 4.
Grease & line cake tin (ideally 9 inch square). Empty sachet of chocolate & add
150g Butter into a bowl and melt over a pan of simmering water.
Note: do not let the water touch the bottom of the bowl.
Beat together in a separate large bowl 4 eggs with a wooden spoon or an electric whisk.
Stir together jar contents and melted chocolate & butter.
Place mixture into cake tin.
Bake 35 – 40 mins.