Sift the flour, baking powder and salt into a bowl. Cream the margarine (or butter) and sugar together until light, white and fluffy. Beat in the egg and almond essence. Stir in the sifted dry ingredients to make a stiff dough.
Form the mixture into balls about 1 − 1.5 inch diameter and place these on a greased baking tray. Place half an almond (split lengthways) on each ball and press to flatten slightly. Brush with beaten egg.
Bake in a moderate oven (350° F / 180°C) for 20 minutes or until golden. Cool on a wire rack.