Australian Women's Weekly recipe for over 20 years and find it totally reliable whether doubling or even tripling the recipe (which is usually necessary as there are never enough cookies)!
half cup white sugar
half cup brown (muscovado) sugar
half tsp vanilla essence
1 and three quarter cups self-raising flour
half tsp salt
125g chocolate chips
60g walnut pieces (we never add these)
Cream together butter, sugars and vanilla.
Add lightly beaten egg gradually, beating well after each addition.
Mix in sifted flour and salt.
Add chocolate chips and walnuts.
Shape mixture into small balls and place on greased oven trays, allowing room for spreading.
Bake at 190-200°C for 10-12 minutes.