Lightly grease a baking sheet. Cream the butter or
margarine and sugar together until light and fluffy.
Beat in the egg, then sift in the flour. Add the
chocolate pieces
and mix thoroughly.
Put 25 teaspoonfuls of the mixture, slightly apart,
on the baking sheet and bake in a preheated oven,
180°C (350°F), Gas Mark 4, for 15-20 minutes until
golden brown.
Leave the cookies on the baking sheet
for 1 minute,
then transfer to a wire rack and leave to cool.