This is a really easy recipe to alter the serving size given it's only 1 part margarine, 1 part icing sugar, 1 part corn flour and 2 parts flour.
Cream margarine and sugar until light and fluffy. Sift corn flour and flour and mix into margarine/ sugar mixture. Knead.
Now you can roll balls and place on oven tray (aka cookie sheet) lined with baking paper, and squash balls flat with fork. Or you can roll dough out on to a floured board and use a cookie cutter to cut shapes out of it. Apparently you are supposed to make them half a centimeter thick (1/5 of a inch), but I prefer to roll or squash them to a 1 centimeter thickness (between 1/2 an inch and a 1/3 of an inch).
Bake at 150 degrees Celsius (300 degrees Fahrenheit) for 25 to 30 minutes. Watch them, you do not want them to go brown, only slightly golden.
(I do not recommend subbing applesauce or oil for the margarine, as shortbread is all about the texture. But, if you do intend to alter the ingredients, then I recommend making a small batch following the directions first, so that you know what the texture is supposed to be like)