Chocolate and walnut brownies

Pre-heat the oven to 180-200ºC depending on the type of oven. Melt the chocolate and the butter in a bain-marie or the microwave and leave to cool a little. Mix in the sugar, eggs, flour and chopped walnuts and pour into the mould. Bake for 10 or 15 minutes. Turn the oven temperature down and continue baking until the top looks crunchy. When cooked, leave to cool and then sprinkle with icing sugar if desired.