Walnut cookies

Preheat the oven to 140 ºC (275 ºF). Grease a baking sheet
with margarine.
Sift the cake flour, bicarbonate of soda and baking powder together.
Add the sugar and using your fingertips, rub in the butter until the
mixture resembles breadcrumbs.
Add the egg and blend.
Lightly press the dough together and shape
into a long sausage about 3 cm in diameter. Chill for 30 minutes.
Cut the roll into 7 mm slices and roll each slice into a ball.
Flatten each ball with a fork and top with a walnut.
Bake the cookies for 10 minutes at 140 ºC (275 ºF). Increase the oven
temperature to 180 ºC (350 ºF) and bake for another 10 minutes
or until golden brown.
Cool on the baking sheets before transferring to a wire rack to cool completely.
Store in an airtight container.