This recipe includes two melted ingredients, chocolate and butter. These can be melted using a glass bowl on a pan of boiling water. It is suggested that you do not melt these ingredients in the same bowl, though this works if you're careful. There can be some curdling and separation if you do this. Also, the cooking time varies greatly according to what shape/size tin you use. PLEASE use your own judgement for this. You have been warned. Preheat oven to Gas Mark 6 / 200 degrees C / 400 degrees F. Whisk eggs and sugar together until pale and thick. Stir in the melted ingredients, then fold in the flour and chocolate drops. Pour mixture into a greased baking tin (swiss roll tin or 7 inch / 20.5 cm square tin is suitable) and bake for 25-35 minutes. Leave to cool for 15 minutes, cut brownies in tin, then leave to cool completely before removing from tin.