Preheat oven to 350 degrees F (180 degrees C).
First put Butter (1 cup) into a large mixing bowl, then add Powdered Confectioners Sugar (3/4 cup). Slowly beat until the mixture is smooth and pale.
With mixer on, slowly add Corn Starch (3/4 cup) and All-Purpose Flour (1 3/4 cup).
Turn dough out onto a floured surface. Knead the dough until smooth. Cut into two even portions and form each portion into a ball.
Fit a piece of baking paper to your cookie sheet and draw a circle with a diameter of 18 - 20 centimeters on the baking paper. Then flip paper over so the circle is still visible and fit one of the dough balls to that size.
Crimp the edge of the dough to make a nice pattern, and then score the dough into eight even wedges. Use a fork to prick the dough. Repeat this for the other ball of dough. Cook in oven for 10 minutes.
Reduce heat to 300 degrees F (150 degrees C) and cook for 40 minutes. It should be a pale golden brown.