This makes lots but you can keep the dough in the fridge and put a few cookies in the oven when you want.
175g caster sugar
110g light brown soft sugar
225g butter
2 large eggs
1 tspn vanilla extract
450g plain flour (less 3 heaped tablespoons)
3 heaped tblsp cocoa
1 tspn baking powder
1/2 tspn bicarb of soda
55ml milk
pinch salt
Beat sugars and butter, beat in eggs and vanilla. Sift in flour, salt, baking powder, cocoa and bicarb. Beat all together, adding some of the milk until you have a soft dough. Shape into 2 sausage shaped logs, wrap tightly in foil or baking paper and put in fridge. Chill for at least 2 hrs.
Whenever you want biscuits, get a log out of fridge and slice rounds off and place on baking tray and cook at 200 deg (180 fan) for 6-8 mins.
You can change these to add different flavourings.