Chocolate Concrete Cake

INGREDIENTS:
160g Butter/Margarine
175g Granulated Sugar / caster sugar
225g Self-Raising Flour
25g Cocoa Powder
1 Egg

DIRECTIONS:
*Pre-heat oven to gas mark 3 / 170C
*Melt the butter, add the sugar and mix well.
*Add the flour and cocoa and mix well until you have a stiff consistency.
*Beat the egg and gently mix into the flour mixture.
*Put the mixture into a greased 30cm x 18cm baking tray, and gently press into the corners and flatten into the tin.
*Sprinkle with a little water and place in the top half of the oven for 45 minutes.
*Then remove from oven and sprinkle with sugar. 
*Allow to cool for 5 mins then cut into required size pieces and place on a wire tray.
*You can either eat it as it is, or make some custard to go with it for dessert.